RonG,
I know for a fact that a 47- 55.1 flywheel and bell housing will fit on a 1958 Chevy 235, so you should be able to bolt on a Chevy flywheel, either 6V or later 12V ring gear on that 6 bolt crank. The only real difference is the number of teeth on the ring gear to match up with the 6V or 12V starter.
HERE is some info on flywheels and starters.
I would think it would be easier to use a 6 bolt flywheel which should be readily available rather than redrill your older 4 bolt flywheel.
