If it's from a passenger car, whcih is what it sounds like, it will not work in a truck. The Passenger rearend was the same from '55-'64, and has an oval shape to the 3rd member and no removable cover on the housing (like a 9" ford. It also has pressed wheel bearings. The Truck diff, however, is only the same from '55-'62 (some '63s may have this rearend as well), has a removable cover, C-clip style axle retention, and the 3rd member and cover are round.
If you can get a pic of it, or get the codes, we can ID it for you before you make any purchase.
