I checked an other manual, TM 9-2320-211-10 (which I found located on the wrong place looking for an other manual). 19230 lbs curb is a M54, payload on highway is 20000 lbs, off highway is 10000 lbs.
Even it is some years to late, dm22630, I tried to help. You did not. And you forgot your JD tractor in your list. Is it a Horicon model? Or allready a Grovetown tractor? Why not a 4x4 tractor?
Wolf