Hello Zuki World, I am doing a mild build, but think I may have some insights to offer that will help pay forward all of the excellent information the Zuki World provided me with. First my Suzuki experience. I have owned three Suzuki's from new. The first in 1992 was an Aqua 4 door sidekick with a little 4 banger and 5 speed for $12,500. 110,000 miles before I sold her. Second was in 1996 a Blue X-90 5 speed for $13,000 which I put 85,000 miles and finally a Suzuki Grand Vitara in 2002 for $19,000 V6 automatic which we put 175,000 miles on. I just retired and my wife, dog, and cat will be touring around the Americas for the next few years. We needed a tow vehicle that a Sprinter based Class C RV will be happy towing. Looked at many used jeeps and for $10,000 you end up with a very tired, awkward to drive, vehicle that is already begging for $. Then a friend teased me about my old X-90 and my reaction was I loved that car! This caused me to reconsider my target vehicle. Additionally I always wanted a convertible Suzuki (X-90 T-top not quite the same). Now of course I am looking for this during the insane used car price increases and yes Suzuki's rising in value or at least people asking a lot more for them. I was obsessed for many months until I came upon this second gen Vitara with only 110,000 miles, and bone stock except for the wheels. As I share more I think you will see why I got the deal I did. Here is a picture of her on the day I purchased her.

She was not smog tested when I bought her so digging into her motor and getting her ready was key. Replaced lots of wear items: plugs, filters, the four ignition coils, valve cover gasket, PCV valve. Noted the oil pan was also leaking, but did not tackle that for smog. She was previously towed and had 5 prior owners. Passed smog with flying colors implying a  much lower motor mileage then 110,000. Now when I test drove the car the PO said that the clutch bearing was going out. Now, this is not what I heard. The noise I heard reminded me of a bad input bearing. After smog I drained and filled all of the fluids for diffs. Looked great no metal. next the transfer again looking good. The final oil draining was the transmission where something happened that I never experienced before as the oil came out there were some loud thumps of items falling in the oil pan. Yep, I was unfortunately correct a couple parts of the input bearing where not where they were supposed to be.

I am willing to do almost anything on a car, but the transmission was a bridge too far so off she went to the local transmission shop for 43 days! Did you know it can be hard to get some of the Suzuki parts? Anyway, I must have been living right because besides the normal transmission rebuild kit we only needed an input shaft and the cover for it. I eventually used Partsouq through Ebay. They got me the input shaft cover. How it works is they get some orders and go to a Suzuki dealership and pick up the parts then they pack them up and send them to you. So that part of my Transmission was purchased in Dubai and then shipped to Italy, Tennessee and then to California. Anyway, they finally got it done and said, "Hey do you know your front differential is not engaging? Oh boy more adventures.

Now that the essentials where taken care of it was time to design my build:
Goals: Reliable, comfortable to drive on regular roads, able to go wherever I want, towable, and able to pull my packmule trailer for overlanding when we want to go where RV's can not go.
Goals I do not have: Rock crawling, mud bogging, desert racing.
Decision time:
Decided to go with 29" tires (235 70 16) on the aftermarket 16 x 7 offset rims that came with her.
Went with the classic coil and strut spacers.
Need to solve the non engaging front diff and go from the aluminum housing to the steel while I am at it.
Under armor as there is nothing. We do not want to copy our RV, but decided we wanted the Zuki to have related tonal colors.
So the main body will be white with front and rear bumpers side mirrors and grill a kind of black dark brown, then getting a new hard top in a tan, and rounding out the wheels and eventual custom roof rack with golden bronze colors.
Using the wife as the color approver I took the goofy "Hot Wheels" and took them to be powder coated. tires and wheel day is always exciting

Next steps were to really strip her back and find out how she has lived. First stripped the interior. Based on the lack of dirt under carpets and such my idea that she had not been off road was strengthened. Now being a California car except for her first two years in Nevada she is rust free so I will not be doing lots of body restoration (outside of paint prep). When I started digging I found what I believe to be a completely untouched suspension system with the original shocks and struts. Also while digging around I realized I also had a leaking oil pan (really bad news for this model) and a coolant leak from the back of a side pipe where there is an O-ring. Many people with the 2.0 4 cylinder have had this issue and asked the question: "Do I really need to pull the diff, power steering rack to change the oil pan gasket?" After my experience I would have to say yes. If you hope to just do it once you will want to pull them both. This was not issue for me as my diff was messed up anyway, and I was completely gutting my suspension and the arms out of the power steering rack needed replacement. But yes If I have to do it again I will pull those things. Some people have disconnected the power steering and just moved it but I would undo it completely. The Suzuki Manual says you also need to disconnect the muffler and raise the motor. This I did not do, But I can sure see why as getting it back in it has to scrape part of the block on the bottom which means if you do not lift the motor you need to put the RTV sealant on after the oil pan is kind of in place. Oh yeah, when dropping the pan next there are three bolts holding the oil pick up tube. have to do that before getting the pan off.
Well here is my first tip for the community. The oil pick up tube has 2 O-rings that seem to only be available with a lower rebuild kit and the O-ring for the coolant pipe can be hard to source as well. Save yourself $ and time and frustration and get the blue metric O-ring box from Harbor Freight. Do not get the red SAE kit as the O-rings for the oil tube will be too thick. But the blue metric kit has all three of these needed O-rings and it cost $7.95. Next two picks show the O-ring box and the motor without the oil pan showing the access you get by removing everything.

O-ring kit

Just my $0.02, with 235/70R16 tires, if you're not rock crawling or mud bogging, the aluminum diff should be fine - that's the size I'm running on OEM 16x7 alloys, there is a minor (and I do mean minor) rubbing on the frame behind the struts when on full lock, and I did trim the back "under edge" of the plastic front bumper to clear the tires on partial lock - your experience might be different if the offset on your rims is different (mine is a +5 mm).

The cause of the non-engagement of the front diff car range from minor things like a loose air line or a broken wire, to a failed air pump, or, if you're unlucky, a failed actuator, which will require disassembly of the front differential.

For me, gathering parts is part of the "fun" of a build. In addition to some of the stateside vendors I have used ebay, and Jimnybits (a parts service in England that has a great selection of parts for the 2nd gen Vitara.) From Jimnybits I have ordered diff drop brackets, a bolt on piece of armor for the rear diff, and interesting attachments that go on the bottom rear shock mount to change the angle of the shock and move it out from the rear diff. I also have my eye on their snorkel, although it would be more of a vanity thing as I do not intend to ford deep rivers. 
Interesting enough the turnaround has been amazing. Made an order on a Sunday and had my parts by Thursday.
The other place I sort parts from is Pick-n-Pull which is a wrecking yard where you do the picking. So many little things like the holder for the hood strut or the grommets and screws for the bumper. Not to mention passenger seat backs and bottoms to replace the drivers. Yes with the Suzuki they are interchangeable.

Just my $0.02, with 235/70R16 tires, if you're not rock crawling or mud bogging, the aluminum diff should be fine - that's the size I'm running on OEM 16x7 alloys, there is a minor (and I do mean minor) rubbing on the frame behind the struts when on full lock, and I did trim the back "under edge" of the plastic front bumper to clear the tires on partial lock - your experience might be different if the offset on your rims is different (mine is a +5 mm).

The cause of the non-engagement of the front diff car range from minor things like a loose air line or a broken wire, to a failed air pump, or, if you're unlucky, a failed actuator, which will require disassembly of the front differential.

I was going to leave it aluminum, but once I diagnosed that issue as a failed actuator it made sense to get a steel if I could. I found a 99 5 speed V6 grand Vitara that still had the diffs. I think the massive mess of oil that covered the front of the donner and the fact it was in a puddle may have put off the other pick n pullers. Thought based on the forum it would be a 4.6 diff like mine but it was 4.3. It looked like the actuator had been installed recently and it worked perfect although this meant that I would have to replace the rear as well so they matched. Anyway, since I had nothing to lose I took my old one to a local jeep shop and I am in theory picking up a welded diff so no more worries and I was always going to put lockinjg hubs as this will be towed four wheels down.

When parts come it feels like Christmas

Here is a comparison of a 1999 Grand Vitara in black and a 1999 Vitara in Aluminum. Note they look similar. A couple of points to help you if you are searching for a steel one. If you can see the color, the steel is painted black and the aluminum is not. Also the aluminum Shows a little circle casting mark above the fill and the steel does not have that.

Note the three supporting fins on the axle housing part of the diff for the aluminum

While the Steel only needs one fin for support. The nice part about the fins is that works even if it is so oil covered that a magnet will not work.

Not all of the aluminum diffs have that casting mark, or the the three ribs, there are single fin aluminum diffs - using a magnet is the best way.

Clean looking rig, nice and straight body!