Tranny swap?

Ok, here's the deal. My wife's Corolla developed some tranny problems, so we bought another (Transplant/victim). Both 3sp AT, both attached to 1.6L 4 Cyls. (One Carb'ed- One EFI.) The mechanic we had told us the two units are NOT Interchangeable. When I inquired about a replacement unit from the dealer ($1900 American) His first question was..."American or Japaneese"? I guess I have one of both, but do any of these factors prohibit such a swap? (I can't believe that the engine or country has that much to do with it.)

Thanks in advance...

um i dont think so, sorry, there might be a small chance that im wrong.

probably the only difference might be electronics (speed sensor, back up light switch) check all connectors, if they are the same, and all bolt patterns are the same, there is not difference.