Jay's page is excellent. The Advanced Adapters guide is worthless and not worth the money - it's just magazine reprints.

I put a 4.3 in my last 86 xcab, backed by a 150 and duals. '88 TBI, rebuilt, AA bellhousing, Downey flywheel, centerforce clutch. Custom motormounts (though i've hard that NWOR mounts work well, especially when flipped upside down), same tubular headers that Jay used, AA radiator, Howell harness and 4.3 fuel pump installed in the tank on the toyota mount....

If you currently have a 4-cyl, you'll need a different tranny. If you have a 3.0 (and a 5-speed), then don't waste your time with the 4.3 - go 3.4.