OK, for the rear it is 66.25" from wheel mounting surface to wheel mounting surface on the Dana 70HD from the 1988 P30. I did not shorten it. to put single wheels on it I used 5.5" of backspacing on a 6X19.5 rim (7" overall with of rim). This makes them fit perfectly centered in the wheel well.
I don't know the measurements for the 1.5 or 2 ton trucks, I don't have one yet, any one want to get that measurement?
To make the axle fit I had to move each spring pad outwards exactly 1" (spring centers of 42") then it works with 2.5" springs as on the 1.5 or 2 ton. If you wanted to use 2" springs like on the 1 ton you would only move them 0.75" each.
On the front end I narrowed a 1994 Chevy 3500HD It started out 79" from wheel mounting surface to wheel mounting surface, I narrowed it 10.25" to have a new measurement of 68.75" and a track with of 60.25" (center of rim to center of rim).
Can someone measure the track with on a 1.5 or 2 ton? I know it is slightly wider than my original 1 ton axle was.
I think these are the right measurements for what I did on the front from going back to my notes when I built it, but I am a little fuzzy, I better go check to be sure what I did.
A P30 truck is really just the chassis that is sold to be put under bread trucks and RVs, that sort of thing, it is a Chevy. Rated at about 1.25 tons I think, but not sure, could be 1.5?
If I were to use the 6X 19.5 wheels, like I have on the front, on the rear the overall with would be 83.75, and the measurement between the inner rims would be 49.25" (these rims have 8.5" of back spacing) and the 8X19.5 tires I used are about 33" tall.
How does this all compare to a 1.5 or 2 ton truck?
