The truck I'm building right now had a 302 in it with a C4. I don't know what kind of mileage it got but the power was always plenty and pulled our small camper when I was a kid. I'll either go back with the 302 or put a 351W in it. Why? Because I can and it's all I need. If I start pulling a lot of stuff I'll go get an F250 or use my '74 with a slightly beefed up 390.