Fuel Efficient '72 Chevy K20

[RaptorSentry]

Looking to get the best gas mileage out of my '72 Chevy K20, it is pretty much stock. The original engine has just recently been rebuilt. This is what I am thinking of doing, if money was no object:

1. Banks Twin Turbo (if it fits, currently they show only '80+, but then say any 350 SB, confusing)
2. Edelbrock E-Street EFI w/ Sump Pump
3. Gear Vendor Under/OverDrive
4. Custom Dual Exhaust 3" Mandrel bent 304 Stainless Steel w/ H-Pipe & Magnaflow Mufflers
5. Replace the old all-terrain tires with some low resistance highway tires
6. Add a tonneau cover to the bed.

Is there anything else I am missing? Is there anything else I can do to improve my fuel economy, other than removing the lead from my foot?