It sounds like you don’t have a 1946 engine.
1942 started the 7/16” bolt size.
If you are staying with the 6 volt starter you will need a 1942-54 216 or 235 flywheel.
I have seen where the 3/8” flywheel holes have been drilled out for the 7/16” bolts.
The center hole is also larger on the early flywheel, but the three dowel pins seem to center the flywheel fine.
