From memory, the 1-ton and standard 1-1/2 ton use the same axle with different hubs. The heavier 1-1/2 and 2-ton use a different heavier axle. The differences in width may be a slight differences in hubs.
Does your truck have Huck or Bendix front brakes? I don't know that brake type changes width, but it could.
I have a '51 4400 and a '52 6400 parked out back, but currently am in no condition to measure the widths. Anyone in the Seattle area want to come to Bainbridge Island and measure them? I'll supply the trucks and tape and might even watch.
