Gas prices are horrible. Engine options???

[mvfd70]

Gas is up to $3.15 a gallon here and my truck is no where near ready to drive. No telling what gas will be when I get my truck done. My current plans are to keep the original I6 and put a 5 speed tranny in it. Can anyone think of a better option for fuel mileage? I want a good comfortable driver out of my truck. It's not gonna be a worker.

I thought about diesel or ethanol and making my own fuel. That might still be an option, someday.

Anyone put a 4.3L in one of these trucks? How well does that work? Any other ideas appreciated.