They are really problematic about leaking around the park cable housing. Are you sure it's coming from the tail housing gasket? That's a terrible picture to get bearings from. I "guess" it's sideways with the bottom being on the left side? I had a 65 with that same transmission for a while and I actually never got it to stop leaking all the way. I slowed it WAY down but there was always a slow drip. But not wanting to drain it to fit it? That like saying "I want to get out of bed without getting up".