Well as far as the older troopers go here is pros and cons, pros are old and cheap, cons are anemic 2.8V6 engine, some folks have converted to 3.4V6 chevy crate engine, fairly a bolt on deal.... Leaf spring suspension and they are top heavy. Newer Trooper has 3.2V6 with about 175HP and 190 ft/lbs of torque, a lot nicer motor for all around use, also that V6 was ahead of its time with distributorless ignition system, all aluminum construction and they can last a while, buddies 96 has 250 000 miles on it and its still going strong. 93 to 94 would net you OBD1 vehicle aka less smog and electrical crap....
As far as the Vehicross goes be prepared to pay top dollar for it, they are rare, another friend owns one, it has same drivetrain as newer Troopers do 3.5V6, 4L30E tranny, full time 4WD... Body parts are expensive to find and it only has 94" wheelbase, Trooper has got it beat on steep climbs and drop offs... Also you can pack a lot more things in Trooper vs Vcross (only 2 seater)....
All in all Isuzus can hold their own, just like any brand, maintain them and they will reward you with reliable service, manual tranny is a tank, auto tranny so so once you start wheeling it hard, definetily plan on getting lower gears for tcase, it helps that auto tranny immensely.
As far as the Rodeo, you get D44 rearend, with 4.10 or 4.30 gears, almost all V6 had limited slip diff (factory code G80 under the hood), 6 on 5.5 bolt pattern, 58" width, front diff is same as troops ( I believe Troopers are little wider and flex a little better in front)......
Love my ZU, got ton of money and time in it, but it was well worth it, when I have it out in Moab, its conversation starter next to your usual Jeep, Toyota crowd.... Right now mine sits on 36x14.50x15 Ground Hawgs which is about limit for tcase output and body clearance I have....
Have fun bying and building and check out our local site
www.zutah.com
Adem