If the four speed in the car now has the 308 bearing with the 4.805 diameter retainer you can just swap it with the one on the OD trans and bolt it in.
Brewers sells new retainers also.

I thought most small block non OD bells were the smaller 4.354 retainer though, so your best bet may be to find an A/F body or truck bell for the 130 tooth flywheel that the OD trans with 5.125 retainer will bolt right onto. May have to change the fork and pivot for a B body though.