Originally Posted by Frank Reiner

Magic:

One thing that may complicate, but not prevent, a trans swap, is the centering method for the clutch housing to intermediate plate. The earlier (pre-Getrag) design has a circular, peripheral centering ring between the clutch housing and the intermediate plate. The Getrag uses two dowels between the one piece trans/clutch housing, and the intermediate plate. To use the earlier trans would require also swapping the intermediate plates, which entails flywheel R&R.