I have a 63 C20 with a 292, 4.10, and 265/75 16 tires. I'd get about 11-12 mpg. I replaced the sm420 with a MY6 and the overdrive got me 15-16 mpg. Basically a stock 292,except RV cam, HEI, headers, Monojet carb. I've heard of even better with major work and a 4bbl.

Larry

I don't own a vehicle that isn't old enough to drink.