Estimated Gas Mileage - Not worried but Curious

Hi Guys - my 75 Dodge Dart Sport Coupe Resto-Mod is almost done, and I'm curious what your "Guesstimates" are on Gas Mileage.

Here's the info:

1975 Dodge Dart Sport Coupe / 318 w/ 500 CM Edelbrock 4BBL Carb / Comp Cams Camshaft & Spring Set (Mid Range Torque - nothing crazy) / Edelbrock Performer Air Intake Manifold / Hooker Competition Headers / 4 Speed A833 OD / Rear End is Ford 8.8" 4.1 Gears.

Since I'm in the Andes Mountains my altitude will be 2500 Mts (roughly 8200 Ft).

Any & All info / Guesses welcome.