I can't help with the brakes not fitting but I can help explain the two piece drums.
When I did the front brakes on my 67 and the drums were shot. We couldn't figure out how to separate the hub from the drum. We finally found an old Chrysler guy that said we needed to use a swedge cutting tool to separate them. We looked all over but could never find one. We finally found an old shop that had one and they let us borrow it. It is basically a hole saw type bit that fits over the stud, and cuts away the part of the drum that is swedged to the hub. We put the tool in a drill press and cut the drum free from the hub. The new drums just fit back over the hub like any ordinary drum would.
Good luck with your brake problem.