It's almost certainly an A904. There are a few 727's around for the slant but they mostly went into trucks and larger cars, maybe taxis too but in any case they are rare. The easiest way to tell is to look at the tranny pan. The A904 has an almost square pan with one corner sliced off at an angle. The 727 pan is larger and has a bulged area opposite the cut off corner. Here's a pic; these are for a late model truck tranny but they look pretty much the same. The one on the left would fit a 727 and the one on the right a 904.
