Sounds like a number of people are rebuilding 77s these days.  I got some good advice here last winter.  Starting to put mine together.

A question on the rear main seal.  Both front and rear cork seals sit in a metal frame with a spring to keep the seal tight, of course.  The metal frame for the front seal has a keyway that fits over a key in the crankshaft.  Therefore the seal has to turn with the crankshaft as it should.

But the rear seal frame does not have a keyway and I'm wondering what keeps the metal frame and seal turning with the shaft. It's a press fit but not extremely tight. 

It seems *likely* it will turn as it should, but I'm wondering if I'm missing something.   Thanks.