160 inch wheel base is a 4400, so if it has the same axle as the 1-ton I think its been swapped at some time in the past. I think a 4100 has the same 137 (or whatever it is) wheelbase a 3800 has and that may be why it uses the same axle.
Does it have the same 5/10-lug wheels on the front as a 6400?
We're talking here about a '55 1st, and my resource on the axle applications is actually from a '51 or '52, but that kind of thing has seemed consistent across years.
I have both a '51 4400 and a '52 6400 and the axles look very similar, though I've never tried to measure either one.
You might look around and see if you can find another truck with a servicable axle. These old trucks with rusted bodies are hard to give away, but could still have some good parts like the axle.
