went out this weekend and picked up a 99 GV for the steel front diff.

was wondering what you guys think of the 2.5L engines. I am putting some 5.12 gears in when i swap the front diff. but wondering if that will bring back enough power in the 2.0L. my 2.0 has only got 140000KM on it, where the 2.5 has over 200.
any thoughts.

Im wondering if that would make a good rig itself? Looks pretty clean. What is wrong with it?

I'm impressed that you are flat towing a GV with a GV!  I guess I need more info on what changes you made on your 2 liter GV to answer your question on regaining lost mechanical advantage/power.  If you added 31" tires, and started with 4.62 stock gears I'm guessing 5.12s ought to put you just about back 'on the money' for loss mechanical advantage, unless you threw on some really heavy mudders.  Even then, 5.12s would have to be an improvement over 4.88 gears if you are running an auto tranny.  I jumped up from 4.62s to 4.88s to run 29" 235 series tires.  I know I would have to go to 5.12 gears to pull 31s to keep from wearing my clutch out prematurely.  My truck has a 2 liter that now has 162K MILES on it and it still pulls strong.  I virtually idled up a 25 foot bank last weekend at about 1500 RPM and never slipped a tire in the process. The jeeps there were cranking quite abit faster to do the same thing(?).   Matching your gears to your tires and attempting to keep your power train at stock or better ratio is important stuff (IMHO).  It keeps the stress spread evenly across your power train versus creating a stress point.

Personally, I am a big fan of the 2 liter engine over the 2.5.  What are we talking here... a 20-25 HP increase in the 2.5 over the 2 liter's (120-127 HP)?  Repair is less expensive/aggravating on the 2 liter.  The water pump placement for example.  Timing chains, for example.  Tear down is simpler.  Better fuel economy of the 2 liter is a gift that just keeps on giving too!  I've driven my father-in-law's ZR2 with a 2.5Liter (pristine OBTW) and I'm just not impressed with the power difference... given the huge difference in fuel economy.  
 
What is your plan for the '99 GV?  Are you going to part it out or what?  IF you do intend to part out pieces, I'd like to have dibbs on both the outside door mirrors.  I agree with tcfootball, it looks like it is in decent shape, at least the body is unless the passenger side is totally wiped out.

I have a 2.0 with 31's and 5.125 gears and I only notice the lack of power at highway speeds.

I bought the GV for parts. Sorry nprecon the side mirrors are one thing i need, i hate ripping the ones off my tracker when in a heavy wooded area, so i need the folding type. i am lifted and running 31's, the main reason i picked it up was the steel front diff. also going to swap the power windows and lock in mine to. the body is really rusty, the two rear mount are gone and the whole rear is resting on the chassis. and all the trim is held on with sheet metal screws.

Things always look better in pics.  Keep us in the mind when you are done pulling parts.  May help you recoup expenses too.  Good luck with the swap!

No prob!  Thank you anyway.  Good luck with all the swap overs!

That's a shame about all the rust.  It looks good in the pics. I'm afraid mine's going to become a parts rig too.  It's got too much rust in the front cross member, (not the bolt in one the main one) 

the main one is a better one to go then the bolt in one, pricewise. you can weld in a front cross member, make it out of some c channel, and gusset the angle cuts and its stronger then factory.