[jeffspower]

I agree gears don't seem to matter on mileage. In my '88 extended cab single wheel one ton, I swapped the 4:10s for 3.21s. Barely made any difference at all, but rolls down the highway much nicer & quieter now.

Absolute best I ever got was 12 driving "MPG style" with a topper on it. 10 most of the time. 6-7 pulling a bumper hitch car trailer with a 5,000 lb. pickup on it.

I rebuilt it a few years ago adding a small RV grind Comp hyd. roller cam, Edelbrock intake, better breathing '96 exhaust manifolds, took the melted down cats out... it didn't improve mileage one bit.

My '72 K20 with 4.10s, Cad 500 and a Qjet does just as good, if not a little better towing.