! tried the 5.38 gears when I was racing my 68 Road Runner in the '70's. They were way too high and I was shifting at 7,200 r.p.m.. They peaked at about 3/4 down the 1/4 mile. The engine was screaming at 7,300 and I was only 3/4 there. I had a 390 c.i. 383-4 speed. I borrowed the pig 5.38 (8 3/4) from a friend of mine who had a boat anchor Road Runner with a 340. For racing I found the 456 - 4.88 worked the best for me. I built my 383's like Chevys and once I used an Isky "500" style cam reground on Mopar blank which worked great. Chevys got power from higer revs and I figured that high revs plus high torque (more cubes) would work. It did, I can tell you!
