Truckasaurus, two different animals, the earlier type is the Borg-Warner, the later type, the all-synchro Saginaw. People HAVE made a 4- speed overdrive from a Saginaw that I know of, don't know of anyone doing it from a Borg-Warner.... requires drilling an accurate hole in the 4-speed main case. It can be done. Search Inliners.org, or someone here might have done it.

Oh, and NO, a B-W tail shaft that includes the overdrive will not bolt up to a 3 or 4 speed Saginaw front main case, two slightly different animals with different bolt spacings.

~ Cosmo
1949 Chevy Half Ton
Rocinante, like Don Quixote, he is awkward, past his prime, and engaged in a task beyond his capacities.
"...my good horse Rocinante, mine eternal and inseparable companion in all my journeys and courses." ...Don Quixote, Cervantes
"If you come to a fork in the road, take it."...Yogi Berra
"Rudeness is the weak man's imitation of strength." ...Eric Hoffer