Just a word of caution about getting involved with a race shop. Lots of these guys have no idea how a stock transmission is supposed to perform, so you run the risk of getting a bunch of high-dollar race parts installed that have no business whatsoever in a street application, and some incredibly hard shifts. Be sure to make it clear that you're not going racing- - - -you just want the transmission to perform the way it did 50 years ago! Lots of times a racing Powerglide has none of its original parts installed, including the case!

http://www.fatsco.net/

I've been buying parts for elderly automatic transmissions from these guys for about 25 years. If they can't help you directly, I'll bet they will know of a shop in your area with plenty of experience on older transmissions. They're in "Noo Joisey", so you probably won't have the same communication problems with them that I always do!
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!