I don't know about track width, but the Eaton HO56 and HO72 was used from '47-'72. I think the one with the Detroit locker might be the one that's the '62-'72, but the basic axle is the same. There are some differences in the brakes, namely that the 1 ton had larger brakes, and the later (at least the '67-'72s anyway) have the drums mounted inboard of the wheel mounting flange instead of slide on like the earlier trucks.

Bill Burmeister