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As for the Trooper Question, great choice!
I had an 89 Trooper and now have an 01 Trooper and love them both. Pretty much the preferred 1st Gen Troopers are the latter years(1.5 Gen Troopers?)
are the 88-91 Square headlight versions. These have the bigger axles and 4wheel disc brakes(the 86-87 had drums in the rear). There is a vague split between the 87.5 and early 88 year troopers that some might have square headlights, but with the older drum brakes and smaller axles.
The Trooper and Trooper II are the same thing so don't worry about getting one that is a II or not. The II was to get around some import law quota or something like that.
The only real choices you have is either the 2.6L inline-4 making 120HP, or the 2.8 GM V6 making 120HP as well. I think the auto trans was only available with the 4banger but not too common. If your handy and since this will be a second vehicle, the V6 might be a better option for you as you can do a GM 3.4L V6 Swap pretty easy. A few members here have done this.
Some bonuses if you can find them to lookout for:
G80 Limited Slip Rear end.
"Wide tire" option. This meant it came from the factory with 31" tires and wider off-set rims.
4.77 gears. Not 100% sure but If you had the wide tire option, it came with 4.77 gears.
*Note* it was first rumored that if you had the widetire option, it came with a G80, this is not allways the case as a few of us who had the wide-tire package did not have a G80 LSD. My guess is that if you did not option the wide-tire package, you could not option the G80.
If it's important to you, AC. It was def. an option and I'm wondering if it was a dealer installed option back then. My trooper did not have AC but most troopers I've seen did have them.
Powerwindows and locks are rare. I've only seen one or two Troopers with this option. Not many Troopers had Auto Trans. too.
There were a couple of "badges" that were around, RS, SE, LS and more, but I'm not sure what came with the packages. The only one I'm pretty sure of is the RS Badge. It was only available in 1989 and this is the Rare Two Door "Really Short" Trooper. This had a shorter wheelbase than the normal 4door trooper. There were 2door Troopers but they were really 4 door troopers but with only two doors(these were the 86-87 models).
My 89 Trooper had well over 180K on the ticker and was going strong. I sold it cause I did not have enough time or space for a project vehicle. Matt from Independent4x.com bought my 89 and there are pics of what it looks like now on his website. If you need anything for your Trooper, contact him first. He has two Troopers now and I think he's getting a 3rd one soon so he knows Troopers. There are other PI Memebers that know alot more about Troopers so I expect them to chime in shortly.