Where is all common leak sources possible on a 65 904?

This one doesn't have a shifter shaft seal. The shifter is a cable that screws into the side of the transmission which I checked today and it appears to be clean and dry. However it has a separate cable just for parking at the back and that's where I see all the fluid. It was such a pain to figure out how to get that cable in and to actually actuate the parking pawl. Now it appears I have to remove it again. I need to do the pan gasket again. Is there a recommended pan gasket that's the best to avoid leaks?