You need the 4BT with everything except the actual transmission, so the adapter, flywheel, and bellhousing from the GM chassis 4BT.
Then a GM manual transmission bolts to it. If using an SM420 the bolt pattern is the same but would need to check the index diameter on the input shaft bearing retainer. The SM465 is 5.125" I think, and I'm thinking the SM420 is 4.937" or something like that? this can be dealt with one way or the other.
In reality an OD transmission is a good idea in most cases.
So before getting wrapped up in using the original transmission consider it's usefulness in the newly converted vehicle.
Grigg
