Take the entire fuel system including the tank, and ALL the wiring even if you don't use the entire harness - its a good source of wire. Also take the coil and dist. for the ign. module.
If this is going into a 250/292 if you get the '81 calif. dist. then its a true plug and play for ign. control.
The Alternator if its good has a decent output rating and much better than the early SI models. The front pulley swaps for a v belt OK.
51 GMC 4.2 turbo Can't solved today's problems using the same technology/thinking that created them
