The Warner T-10 was built by adding an idler and a reverse gear to the rear housing of the T-85 heavy duty 3 speed, back in about 1957. A lot of Pontiac factory race cars ran the T-85, as it was much stronger than anything Muncie was producing at the time. That made room for an extra forward speed in the main box. I remember the advertising campaign Chevy kicked off when that transmission became an extra-cost option for the Corvette and a few other factory hotrods. It came along about the same time as the Rochester fuel injection system on the then "new for 1957" 283 engine. Chevy built a few fuel injected "210" 2-door sedans with the T-10 for drag racing- - - -lightweight low-bucks bodies with the Corvette performance package. The supercharged Ford 312's ate their lunch at the drag strips anyway!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!