The hydra-matic trans input shaft is actually supported by a pilot bearind or bushing in the back of the crankshaft. There is no balance issue that I know of on the flywheel. As mentioned, there is a runout check on the flywheel face which would apply to any flywheel. Then there is the runout check of the opening to make sure that trans input shaft is centered with the crankshaft. That is the one that would be corrected with offset dowel pins if needed. Think of it this way, In 1954 if a block froze and cracked, the dealer would not have scrapped the whole driveline. They would have replaced the shortblock, checked the runouts and corrected with the offset dowel pins if needed and sent it on it's merry way. I expect that the dowel pins would be a job for a machine shop now if needed. I doubt that they are still a stocked item at the parts counter.
