[Shyguy]

There are many ways to increase the mpg on these old trucks, but don't expect to get as good mileage as the newer trucks that are fuel injected with over-drive transmissions.

You did not give a lot of information about the setup of your truck. Addition of a HEI distributor, headers with dual exhausts and well tuned carb are good starting points.

If you want to spend more money you can go with an overdrive transmisson like the 700R4 with a 3.43 or 3.73 rear-end.

Many people on here can give you more info on what other things to do to the engine.