Bill,
With the exception of slant six or some oddball transmissions, here is how to ID most garden variety TorqueFlites:
Looking at the engine mating surface, the top two bolts (other than the center hole, if one is present) are about 7 3/4" apart. B/RB transmission holes are just under 6 1/2" apart.
V8 Transmissions have the starter in line with the centerline of the crankshaft. Slant six transmissions will have the starter mounted high on the driver's side of the bellhousing.
Looking down the pan rail on the passenger side of the bellhousing, 904/500/42RH transmissions will have a straight pan rail, where the 727/518/46RH will have a bump where the front servo is, which will also have the hole for the dipstick.
Sighting down the driver's side of the transmission, early ('62-65) transmissions will have the 11/16" hole (angled toward the front driver's side corner of the car) where the shift cable enters. Depending on how the transmission was removed, you may see the adapter for the shift cable inner member in the center of the hole. Looking farther back, you will see the lone stem for the kickdown linkage sticking up from the case. '66-up transmissions won't have the shift cable hole, and will have the larger "D" shaped shaft that connects to the manual valve lever surrounding the kickdown stem.
Hope this helps!
SC