So you're asking the same questions in two different threads...
The rear under your '46 and the rear from a '64 are the same rear. The pumpkins will swap and you have the same very limited options for ratios.
The GMC 302 will bolt to the Chevy bellhousing. You'll need the GMC flywheel. You will need to drill new holes for the front mounts. Check the Tech Tips section for more information on swappnig the 302.
