Um...not sure about the 153 tooth pre/post deal John. Not that it really matter's as it relates to your post, but if the flywheel doesn't fit I'm thinking it's because of the later style being a one peice rear main seal. About your question, not 100% sure but thinking he may need to change to a 10¼" clutch & maybe even smaller bellhousing. I'm not an expert on production style clutch/bellhousing combo's but what your mentioning is ringing a bell to some degree...
. Wish I could be more sure for you. Bellhousing should fit for sure unless it's an early 283 one...then I can't say 100%, very early ones may, may be smaller, (50's to early 60's).