Just measured an AD 1 ton:
* Spring centers are 41.5" apart (with the springs as narrow as possible)
* Width outside of springs is 43.5"
It's cold out there!
These measurements were made on a '54 GMC 1-ton that currently has a 14-bolt in place under it. My pretty much original '54 GMC has enough stuff stacked on it I can't easily measure it now.
I get spring centers at 41.5 inches actually measuring from the near side of the head of one spring bolt to the far side of the other.
I get the outside spring measure as 43-5/8 inches but mine is all bolted together so there is no easy give.
That measurement does not account for the ubolts. I see three or four inches on each side between the springs and backing plates with my wider rear. Since the difference in width is only three or four inches I'm surprised you come up with so little clearance between springs and drums.
With only 3/8ths on a side I'd worry about the the ubolts clearing. If its 2-3/8ths then it should be no problem.
