http://www.steelsoldiers.com/showthr...y-part-numbers
Check out this link above. Talk about perch widths. Basically it's a late 70s to 80s 14 BFF Axle. If it has brackets welded on for disc brakes, it's common to use front rotors and 70s Cadillac calipers with a lever for the emergency brake portion...
Detailed pics with the wheel off will help ID what you have. You may also have to measure backing plate to backing plate to see if it came from a Single Rear Wheel (SRW), Dual Rear Wheel (DRW) or a Cab and Chassis (C&C).
A cab and Chassis would have been ordered from the dealer as a truck with no thing on the back frame so the end user could build something.