I have a '54 Tudor Sedan "P Code" car with 256 Y Block engine. It had a standard 3 speed transmission which I am replacing with a 3 speed overdrive. The car has 3.90 gears in the rear axle now but I have the 4.10 "pumpkin" which was in the car from which I pulled the O.D. transmission. In my experience, Ford usually fitted the O.D. cars with the 4.10 gears. What are the advantages or disadvantages of leaving the 3.90's in the car after the switch to O.D. vs. replacing the "pumpkin" with the 4.10's? Thanks, Alan S. Freeman