They're few and far between, and expensive to boot. Unless you're working with a factory original H-M truck, swapping from a manual trans to a hydro is a huge job with not much chance of success. If all you want is an automatic instead of a standard trans, it would be simpler, and less expensive to retro-fit a 6 cylinder Stovebolt to a Powerglide, or possibly a Turbo 350. Stay FAR away from a 700R4/4L60!
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!