i know the truck has a dana 60, but what axle type, gear ratio, and whether it is a single or positive trac. I want this rear axle to go in my 79 bronco with a 466 big block

 

Is there a tag under one of the bolts on the rearend?

 

The first two digits of the axle code (C3) give the rear axle style, ratio, axle capacity and whether it's limited slip or not.

But there is no C3 axle code listed for a 1981 F250. Only 1980 and 1983/89 use this code.