[Russell]

1 ton trucks have different frames than 1/2 and 3/4 ton trucks. Becuase of this, the spring perches on a 1 ton are located in a different spot than the 1/2 ton and 3/4 ton perches are.

3/4 ton and 1 ton 14 bolts are the same thing, both are 10.5" ring geared full floating diffs. Only difference is in the spring perch locations.

If those diffs are a matched set, and the front is a D44, then it'll be a 3/4 ton rear diff. The 1 ton trucks got D60s (not sure when their production run started, sorry)

To find out for sure, just whip out the measuring tape, measure from centering pin to centering pin on your current 10 bolt, then check to see if it is similar to the 14 bolt's. A little bit of sideways variation is normal, you can move the leaf springs side to side a bit.