After even more research, I have heard MANY different things. Comparing the 904 and 999, I have heard the cases are the same, OR, the 999 has a larger bellhousing, OR all AMC's used the same case including the 727, OR the 999 has two ribs above the rear servo, OR the 999 was lockup only. I am about to give up on net research. All I have is the numbers to go by, and I'm not sure the dealer will be able to help. I've got the numbers to go by and if I could find some way to count the first gear ratio short of tearing it apart since the 999 has 2.74 and the 904 has 2.54. At least I've learned only the ENTIRE history of the "Legendary Torqueflite Transmission." Ha. Well if anyone has any idea, I would love to know, really I would. But if not I'm just going to call a dealer and see if they can help. Thanks anyway.