I have a complete differential from a 65-67 Mustang/Cougar. Actually the date code is 6CD and the tag is WCZ-E. It's in San Francisco and heavy but is fine. I also have some other 7>75 and *" pumpkins but I can't get to them quite at the moment.
I never cut anything but I do put a hatpin in the rear cork to keep it from falling inside the pan. I put a SMALL dab of silicone on the rear arch to side gaskets and that's it.