Actually it is quite easy to use the diesel one. It has been a few years (more than 10 actually), but here is what I remember (mine was in an 82, yours may be different).
Basically, remove the glow plug wiring (snip). Pull the pink wire out of the harness at the rear of the engine and plug it into the distributor (it is already there). Alternator and starter should wire up fine.
My worst problems were completely removing diesel fuel from the tank (had two full ones) and getting the emissions guys happy (mostly from a "recertification" standpoint). Use a complete 350 from the same type of vehicle (GVW rating for emissions, same year or newer, etc.). Unless you don't have emissions... then just count your lucky stars!
If you have the factory harness for the 350 already and want to use that, PM me. My factory manual is very tough to read on the wiring harness connector so it would take a while to verify the wiring compatibility. In a nutshell, though, the wires should all be the same color. The diesel might have a few extras is all (glow plugs and a few other sensors). I was surprised at the wire color compatibility when swapping in my Vortec 454 from a 96 pickup.
Probably too much info, but a few other notes:
Power Steering (presumably hydro): just tee the return line back to the pump; the diesel pump mounts differently and will not work; 350 pump only has one return line.
Alternators: Mounting is clocked 1/4 turn; remove casing bolts and rotate (or use the one from the 350)
Exhaust: Complete bolt up; easy as pie (as long as the emission jockeys don't ask for kitty cats).
Hope this helps.
