X2^^ Nice Truck!
Someone may have swapped in the 55P Passenger Rear.
55P >> http://www.ringpinion.com/DiffDetail...ir&Diff=GM+55P
55T >> http://www.ringpinion.com/DiffDetail...D)&Diff=GM+55T
I don't know of a direct Bolt In upgrade Rear. A 8.5" Camaro rear, Ford 8.8" will work with Mods. http://www.therangerstation.com/tech_library/Axles.html
9" Ford, I think these are Drum to Drum measurements>> http://www.therangerstation.com/tech...InchAxles.html
More Drum to Drum Widths >> http://carnut.com/specs/rear.html