Very well covered CTH. The only thing I would add is that the original cranks for manual trans aplications have a different number than those intended for automatics. The most obvious difference would be the area where a pilot bearing sits on the manual trans or the torque converter nose is supported on automatics.
I would say the risk should be equal, through engines of that era (since they use similar pilot bearings and torque converters) and I know that I have done this on Diesels with no machining. I am not sure we supported the torque converter properly; but I know of no subsequent problems.
I have also worried about the balance, especially due to the vast difference in weight between manual and auto flywheel assemblies. Since the ones we did exhibited no problems I have to assume that even though the crank assy is balanced as a unit the individual parts most be close to balance. Balance could be more important on high revings gas motors.
The original chassis 116.02x auto trannies were 722.1 with 4 spds.
Bosch Master, ASE Master, L1
33 years MB technician