Another reason I asked the above question was that my 1970 Plymouth GTX has an 8 3/4 rear end with 4.10 gears. I put a Gear Vendors overdrive on the 727 transmission and now the final ratio is about 3.21. It has the acceleration of the 4.10 in the first three gears but the highway gear of 3.21 in overdrive. I guess that is where I don't understand the gearing in the new Challenger.