My replica gets between 22 MPG and 25 MPG on the highway, putting along about 70 mph.
My drivetrain is (I THINK) a box-stock 5.0/HO engine with the T-5 transmission out of a 1989 Mustang GT, just converted from FI to carb.
3.70 gears, 0.63 overdrive, 2.95/50X15" tires on 15" Cragar Drag-star wheels.
Before I got the car it had a 780 CFM Holley on it, reportedly ran like crap and got very bad gas mileage. Right before I purchased the car the previous owner switched to the Edelbrock Thunder (575CFM, I think) and it runs great now.....you might want to check your carb.
...and, I'll second the recommendation that you spring for a good tune. It can be the cheapest horsepower you'll ever buy, and get you better mileage at the same time.
Cheers!
Dugly
