Paul and Carl:T85, T86, T89, T96, T98, T10, etc are just a few model numbers of transmissions built by Warner Gear Div. of Borg Warner in Muncie IN. The GM "Muncie" 4 speed transmission was built in the "Chevrolet Plant" in Muncie too. Sadly, the GM plant is now empty, and the Borg Warner plant is in trouble. They build transfer cases for Ford, and with Ford's huge cutback, well, you can guess the outcome. BW in Chicago will have a corporate meeting this month do decide whether or not to close the Muncie plant.
Anyway, the above model numbers were built for many different car and truck makers. Inputs, outputs, bolt patterns, and mounts varied with each manufacturer's needs. My friend used to drag race a '51 Studebaker in stock class, and would take the top cover off his Stude trans and install a jeep floor shift lever. Ingenious, yes, but you have to know him. He still has his '51, with twin turbos on a 289 inch Stude engine and gm turbo 400 trans that goes low 10s and 140+. Back to the transmission. Many of the internal parts are the interchangeable, such as gears and synchronizers. There were only two basic overdrives, R10 and R11, light and heavy duty, and all the "working" parts of each model were the same. I knew they guy who invented the OD for them, and he got $1 royalty for each one sold. Sorry for the long post.
John