really nice truck !
good looks, and great stance !
if i'm figuring correctly, the A518 has a .68 overdrive.
with that said, you 4.30 gear should be a 2.92 in OD 4th gear.
that's a pretty good cruising gear in my stupid opinion.
the rear tires should be at least an inch or so loaded diameter, plus an extended roll-out circumference,larger than the factory size tire, so that should add to the lower cruising rpm as well.
what guys seem to forget, your engine needs to be in a good rpm range that allows it to use the fuel efficiently as it is able.
too low an rpm and the engine lugs, even with more footie on the gas pedal, which causes lower fuel economy.
too high an rpm and the engine runs good, but you have it eating more fuel than necessary.
you need to find a happy medium where the engine vacuum is very high, or as high as you can get it, and your footie is just touching the gas, thereby giving the best possible gas mileage at the least possible rpm.
timing plays a HUGE part in this as well, so don't be afraid to start playing around with this, either by distributor modifications or playing with a laptop.
just my opinion. your "mileage" will vary. []