I hate to disagree but I have installed the center section from 55-62 1/2 tons into 40-54 1/2 ton axle housings many times. They even use the same axle splines. The standard ratio is 3.9 which is not that much better then 4.11. There was a 3.7 option starting in 58 but it is rare. The auto ratio was 3.38 which Patricks reproduces. You will also need to remount the housing to the springs with solid pads.
