Check Ebay for shop manuals on that transmission- - - -there's usually several ads for either originals or reprints. With very few exceptions, any manual for Cadillac, Pontiac, Oldsmobile, Nash, Chevy or GMC (truck) will have enough information to do a good rebuild. The manual you're looking for is for the "dual Range" Hydramatic, from about 1953 to 55 in the cars, not the later model "Controlled Coupling" transmission that was used from 1956 to 64 in cars. Chevy or GMC trucks never used the controlled coupling transmission. It's entirely different from the dual range, and it's a real PITA to rebuild.

The best source for antique tranny rebuild parts I know of is FATSCO transmission parts.

http://www.fatsco.com/index.htm

The dual range hydro is VERY picky on throttle pressure adjustment. Too high, and it slams into gear, too low, and there's lots of slippage and clutch burning. Be sure your tech knows all he needs to about making those band and throttle linkage adjustments.
Jerry

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