[Tony Janes]

First of all you do not want to turn a 400 Pontiac 7200 to 7500. Build the car as a 1972 Grand Prix with the 250/315 455. this would make it a H,I and JSA car.4.33 or 4.56 rear end gears, shift 5400 to 5600. 5800 to 6000 thru the lights.455 is much better combo than the 400.