it doesnt say who made it. my guess is getrag. it has a pretty comprensive breakdown of it in the haynes manual for the 280, 1977 to 1981. probably four pages showing how to measure wear on the synchros and how to take it all apart. it looks like it may be all that you need.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.