As far as the 4.3L being sold in the Hombre and the only GM C.A.R.B allowance, you forgot about the 1st gen trooper v6 (2.8L uggggggghhh) gm motor and the 3.1L in the 91-92 Rodeo and 91-94 Pup 4x4s.....anyway...im stuffing a 1989 Caprice 9c1 350 v8 police motor in my 1992 Isuzu Pup 4x2. The wiring harness is soooo simple to swap over its not even funny. You can get a wiring harness for the engine from Painless wiring or Howell Engineering for under 425.00 that is a stand alone unit. You plug in the harness to the motor and to the ecm, throw 12v from the ignition switch to it and VRRRRROOOOMMMMMM. You already have Fuel Injection so the TPI unit already has enough fuel pressure. The motor mounts will need to be fabbed and if you want to keep the 4wd, just need a 700r4 trans or 4L30E (4L60E also) and a GM transfer case and custom length drive sahfts (about $60 each to make). The hardest part about this swap is getting the motor to fit in the engine bay, keeping the A/C, which brackets can be made to adapt the Isuzu compressor to the GM block. Cooling might be an issue as well, but not of this can't be solved, with enough time and effort this swap is not as hard as some people would imagine. Kudos to you and good luck with the swap.
Regards
A HUGE Isuzu fan
Ron