The small block transmissions have the same bolt pattern 727 or 904.
I think either would work.
My spider senses are tingling telling me that it was meant for a 727 though.......
I haven't seen one so I'm just guessing when I say this, even though they have the same engine bolt pattern the 904 bellhousing is a little smaller and uses a smaller converter so they might not interchange. My other guess would be that you are correct in that it was meant for a 727 as Ma Mopar generally never installed 904's in trucks, even behind a 6.
