Here's a Trooper 4.3 build FYI:
http://www.off-road.com/aimages/articlestandard/isuzu/452005/194437/article.htmlA ton of $$$ and time went into that one! As I recall they had access to the now-Unobtanium Advance Adapters 4.3-to-MUA-Isuzu kit; they no longer make that one.
Here's a 4.3 into '94 Trooper build thread at the Planet:
http://forum.planetisuzoo.com/viewtopic.php?t=42413An old thread, a little talk, maybe you'll get some ideas. I don't know if he ever got it done:
http://forum.planetisuzoo.com/viewtopic.php?p=194632Note that the Isuzu MUA5 manual trans in a V6 Gen-I rig has a bolt pattern to fit a 60-deg GM V6. The 4.3 engine won't bolt up to that trans, nor will the MUA bellhousing come off, as it's an integral part of the transmission case.
You'd need to swap-in the entire 4.3 drivetrain and do all the necessary mods for that. Easier, from what I understand, if you do a body lift. Hopefully the 4.3 transfer case has the driveshaft coming out the pssgr's side, or there'll be more mix-n-matching required. Plus the wiring for the Vortec V6, which is totally different than the Troopers TBI-system wiring.
Your option for an easy swap would be a '93-'95 Camaro/Firebird 3.4, it'll bolt right in. 160hp with a carb (more with modded TBI), around 190 torque, lighter and smoother than a 4.3. The 4.3 does have an advantage on torque but I think my '90 LS with a 3.4 rolls along very smartly!
With performance-adders such as a larger TBI, bored intake to match, 1.6:1 roller-tipped rocker arms, a Comp Cams "252" performance cam, and 2-1/2" exhaust, you're looking at probably 180+ hp and excellent torque.
Note that a GM 3800 RWD engine would bolt right up to the MUA tranny as well. You'll find those in '96-up Camaros/Firebirds. You'd have to rewire the EFI system and of course all accessories, flywheel, plumbing, etc etc. The 3800 has around 200hp stock.
The 3.4 swap is no more complicated than a 2.8 R&R, with the exception of a bit of drilling for the driver's side starter mounting. And you can purchase a drilling jig kit for around $80 from Rodney Dickman Fieros that makes the mod a cinch.
At any rate, a 4.3 swap can be done, just with some $$ and quite a bit of labor.
There is a lot of swap talk at the Planet, so you might search around there for some swap threads. They have a Search feature which should turn up plenty of results.
http://forum.planetisuzoo.com/index.phpHTH...........ed
The earlier TBI models are a little lower in HP but MUCH easier to wire up and work with. Its not gonna have much more HP than your 3.2, but the torque curve is a lot better. You'll need to swap the whole drivetrain though, and IIRC chevy didn't run any passenger side t-cases so you'll have to adapt to another t-case (eg. the D300 I run). 
