Back when I did my swap, I too tried to find an ideal donor vehicle. I finally settled on the first vehicle I found with a good 350. I purchased a 91 G-30 one ton van from a local electrician company. It had a rebuilt 350 with about 30k miles on it and a GM remanufactured trans. I paid $550 for it. I pulled the motor/trans and found I didn't want to use the trans, 4L80E. But I did get a lot of bracketry and parts. I sold the van body for $150 and the trans for $500. That gave me a good 350 with many parts and $100 in my pocket. Also, Grumpyvette got the aluminum driveshaft from the van.