So let me get this straight. You want advice about swapping engines but you haven't even replaced a window motor in said truck? The window motor is VERY easy. I replaced mine out of Junkyard truck. I did 2. The AC? Any idea why it doesn't work? Could be as simple as recharge... And yes valve seal replacement will fix smoking. I have 1990 3.0LS and 1995 3.5SR. Personally I don't really notice that much difference in power. The SR is nice but I would much rather have 3.0. The SR DOHC Motor is WAY more complex-pain to deal with. That's my 2 cents.

1990 Black Monty LS Over 300K' 1993 Isuzu Rodeo LS 4x4 46k (yes only 46K!)1989 Honda Transalp 600 Africa twin,