Apparently I got a 72-up rebuild kit for my 71 904. Now it's open and non-returnable. Looks like the lip seals for the rear drum/piston are correct and went in just fine. Inner lip seal was the failure point last time, and I'll confirm when I can air test. That brings me to the front drum/piston/seals. Obviously this was a change between 71 and 72. Question is can I interchange a 72-up 4 clutch drum with no problems? Or do I need anything else? I have access to a bunch of used parts and there should be 72-up drums there.

This unit had previously been rebuilt so I can't assure that all the parts are the ones that came in it from the factory. Casting dates would lead me to believe they are correct.