During the rebuild of my engine I found a few other issues to deal with, power steering pump being one of them. Replaced that ( 3 times  ) and now I want to replace my resivior which is weeping around the pinched seam. Went to the upuillit to find a replacement and the only one I could find is questionable at best. It was full of rusty water and what paint was left was covering a thick coating of surface rust.  I looked around for some other vehicle that had a remote res like ours and found this on an Isuzu Amigo:

The one on the left is the Isuzu, right side is the stock one. They are almost the same diameter, but the Isuzu one is at least a third taller and holds that much more fluid, which I think would aid in fluid cooling. The nipples are the same size, important because finding replacement hose in this size ( not 1/2, not 5/8 but 14mm ! ) is near impossible and my hoses are still good. The only issue I can see, if it even is an issue, is the placement of the nipples on the Isuzu. The suction feed line and return line are reversed in placement: Feed line to pump is off the bottom on Isuzu with return line above it, reverse of the stock Zuk res. I don't think this will be issue but any opinions or actual knowledgeable input would be helpful. So, what do you think?

I would guess it should work fine.  Afterall, it is just a reservoir. 
Personally, I would take a metal one, over a plastic one, but that's just me. 
If you wanted to try to fix your old one, you could probably clean it up good and JB Weld around the seam and repaint it and it should work and look fine.

I probably clean and refinish the outside of the junk yard one, but the rust INSIDE is gonna be an issue. JB weld on the seam of my original may or may not seal it. Once it's contaminated with oil, it would be damn near impossible to get all the oil out of the seam and make it clean enough for a good JB weld repair. As long as it'll work I think I'm going to try and fit the bigger one. 

I probably clean and refinish the outside of the junk yard one, but the rust INSIDE is gonna be an issue. JB weld on the seam of my original may or may not seal it. Once it's contaminated with oil, it would be damn near impossible to get all the oil out of the seam and make it clean enough for a good JB weld repair. As long as it'll work I think I'm going to try and fit the bigger one. 

Yeah, if the JY one has rust on the inside, I wouldn't even try to use it.
Brake cleaner should clean up your old one.  If you JB Weld it, you would be trying to contain the leakage within the JB Weld, not necessarily seal the seam.  You could always use a torch and burn the oil out of the seam too, before you try to seal it.
I think the plastic one will work ok, I was just giving you an option on reusing your old one.

The plastic resi will actually cause higher fluid temps even with the larger capacity, the plastic is an insulator whereas the metal conducts heat away and releases to the atmosphere.

I have yet to ever see a metal power steering resi not weep fluid, LOL

shim the pump and add an cooler for the PS...

I am tapping my box to go partial hydro < $100

I am using a plastic tank on my PS just like your Amigo one, that I thought came out of an XL7.  I then ran a loop (approx. 14") of aluminum tubing (from AC lines) in front of radiator that I routed the return line through. 

Now that is a decent idea!

How about using some aluminum tubing, wrap it around a 2" dia pipe a dozen or so times and then slightly flare the ends to help hold the rubber lines on,,,added volume and cooling

...or a small trans cooler from the pick n' pull

that is a three+ hour round trip just driving........

that is a three+ hour round trip just driving........

..same here. They won't even let you walk the yrd by me...'liability' 


Gas it to expensive to pick used parts, lol.

SO-

new, 30 bucks, shipped:

http://www.ebay.com/itm/Universal-Trans-Cooler-/121007909578?pt=Race_Car_Parts&hash=item1c2ca22aca&vxp=mtr

All good suggestions guys, especially like the " tubing " cooler addition one. Frankly, I really don't think I need a PS cooler, been running this truck without one for almost 6 years with no ill affects. If it wasn't for the leaking seals the old one would still be in there. I'm trying to simplify, adding external oil lines for cooling just makes for more shit to go wrong, and with my luck it probably would.  ( We are in the middle of a hurricane, all businesses are closed, roads closed to the public  AND MY FRIGGIN WATER HEATER JUST TOOK A SHIT AND IS LEAKING!!! I WON'T BE ABLE TO FIX IT UNTIL THE STORES OPEN UP AFTER THE STORM. NOTHING TO DO WITH THE WEATHER, JUST BAD TIMING AND MY LUCK. GO FIGURE    )
 The res thing, well I just don't like leaks. It's such a small amount it only looks a bit shiny around the seam, but gobbing it up with JB weld, even though it would probably stop it just isn't my style. I know it would work, have done it on other jobs, but no JB this time. I bet ya Sky, you could probably make it look good too. 
I never took into account how the tank itself could act as a heat sink. I think that with a third more oil in the system though any deficit in the tank cooling itself would be a wash.  If the plastic tank is not up to the demands of a 4WD, why would they put one in a 4WD Isuzu trooper?   I don't have any reservations about the tank being plastic, and for $5 the price was right. I've seen fancy billet aluminum ones for way over 100 bucks, but this aint no show car. 
If it fails somehow, I'll let you all know so I can be publicly ridiculed   

I'm running a loop p/s cooler, been on there for about 60k and still on my first  pump(although its seal is starting to leak at this point). Route your lines and hoses so they won't rub and wear through,  and you're golden.

I understand and concur about the nasty looks of a weepy resi, mine is weeping and it bothers me every time I open the hood, also when all gobbed up with JB weld it wouldnt look very nice, but the JB Weld can be sanded and top coated.

Also another route you could try is to clean the metal resi and apply black Chassis Saver, it will seep into any cracks and seal them up. Or applying solder to the seams to seal them would have even greater hyd fluid proofness

All good suggestions guys, especially like the " tubing " cooler addition one. Frankly, I really don't think I need a PS cooler, been running this truck without one for almost 6 years with no ill affects. ...
  If the plastic tank is not up to the demands of a 4WD, why would they put one in a 4WD Isuzu trooper?   I don't have any reservations about the tank being plastic, and for $5 the price was right. I've seen fancy billet aluminum ones for way over 100 bucks, but this aint no show car. 
If it fails somehow, I'll let you all know so I can be publicly ridiculed   

Last year at Zukafari one of my rubber trans cooling lines crimped, causing Trans. overheating, then motor overheating, PS puked out, ARB air lines melted etc.  And then the PS box started leaking.  So part of my fixes was the tubing loop for some cooling, and a larger reservoir.  Having the 12mm aluminum AC tubing setting in scrap metal barrel made made it a natural for improvised cooling loop.  I also had the slightly larger plastic tank laying around and my 93 tank was always oily so I made the modifications.  I haven't had any problems this year (which is not that much time).