Getting the cam, rockers, cam housing, and cylinder head off is straight forward. The head stud bolts were on extremely tight. I had to use a 6 ft. breaker bar. When it comes to re-assembly, the factory manual calls for tighening to something like 15 ft-lb and turing it 90 degrees further. I don't know how tight this would be, or is it enough.
Anyway, after you get the head off, you will notice that the later 964 models have a sealing ring between the cylinder and the heads.
Don't just write on the cylinder heads, when you send it in to be rebuild. Everything will be cleaned off.
Back to the cylinder head ring, it is a .75mm graphite-aluminum-graphite gasket. I used a small wood chisel at a shallow angle to dig it out. If you just scrape off the graphite, you did not remove all of the gasket. The gasket itsef is .75mm thick. Cleaing it is a pain.
Another difference is the 964 uses a green viton rubber o-ring for the cylinder base gasket insted of copper.
