Try
www.phoenixhardparts.com or ebay. You don't have to spend 1500 bucks, to get a new tranny with a warranty that's done right, too.
Most (including AAMCO) transmission shops will install other Transmission company's transmissions, but you don't get a labor warranty from them, you'll get the labor back if needed from the rebuilder.
This is NOT an ad for Phoenix Hard Parts, I just had a friend who had one installed at an AAMCO shop last month. He paid under 1000 total, but he did have to wait for a $250 core charge back from the remanufacturer, (which he DID get back!).
I do have a "mail order" 41TE trans in a '90 daytona that my father in law has now... after 5 years, and still kickin'!
This doesn't mean you can't get burned by shoddy places, but I haven't yet, (but I check them out as carefully as I can!) so, take it only as my opinion!
Slantsixness