About 15 years ago, I had to put a new engine in my daily driver '82 GMC 1/2 ton. Only thing I had laying around was a just rebuilt 283 shortblock. I scrounged up a 305 parts engine and ended up with a 283 with 305 heads (those got a valvejob) and the newer brackets, etc.
With headers, dual exhaust, Edelbrock performer intake, 390 Holley 4-bl, 3-spd manual and a 2.73 rear end, it'd push 25mpg with the tailgate down.
