The reason for the matched halves of the bellhousing is to be sure that the torus member of the fluid coupling runs concentric to the crankshaft hub. The torus is the part that some uninformed people would call the torque converter (which a Hydra-Matic does not have). You'll need to fabricate a fixture to check the front of the bellhousing when it's bolted to the block by rotating the crankshaft and checking for runout with a dial indicator, then you'll need to bolt the two parts of the housing together, rotate the torus, and check for runout there. At one time, I believe there were offset dowel pins designed to compensate for out of specification dial indicator readings. Very few shops had the equipment or the knowledge to correct an out of spec runout situation, even back when these transmissions were in general use. Since my father was the first man in Nashville Tennessee to work on automatics back in the late 1940's, his shop was the exception to the rule. The checking equipment can be fabricated with a little ingenuity- - - -the skills needed to correct a problem haven't been general knowledge in about 50 years or more!
Jerry
