MILEAGE possibly the most sophisticated topic moparts could tackle. I had a 318 2bbl in a 84 dodge with 3.23 gears and 35 inch all terrain tires. In this state of tune it got really bad mileage city and highway. Swapped to 4.11 gears and the mileage was greatly improved, RPMs are not the only or even the most important factor for mileage. My Duster with 4.30 gears and 28 inch tall tires, 727 and a 340 would get 14 15 on a road trip to Fallon 150 mile round trip. While I was there made 2 passes at the drag strip. Same Duster 422 ci small block 3.23 gears 28 inch tires 5 speed OD 1800 RPM at 70, 20 to 21 MPG if I am law abiding. The 340 didnt mind the RPMs the stroker really wants to be put to work. The things that I am certain about is run as much VACUME advance as possible with out detonation. Keep tires inflated as as per tire manufacturers suggestion and drive gently. This is an INTERESTING thread keep up the good work peeps.