1965 small block A904 leak

I have a pretty bad transmission fluid leak in my '65 Barracuda with a small block and the correct 1965 cable shifted A904. I'm pretty sure later years are different and probably easier to fix. The transmission was fully rebuilt last year with all new gaskets (by someone else). I started the engine for the first time a couple of weeks ago. I cleaned everything with brake clean and looked with my 10 dollar Amazon borescope where it might come from. I didn't have to wait long to see it seeping out. Below you can see it on a screenshot. It's at the bottom of the extension housing gasket where its bolted to the transmission body. I might be just a bolt that needs to be tightened. If you're looking towards the front, it's the bottom right bolt. You can't see the bolt - it appears you can only access the bolt from the inside of the parking lock cable housing.

I would like to confirm that the bolt can only be tightened from within the parking lock cable housing?!

I don't really want to drain all the transmission fluid and find that parking lock cable housing gasket etc. Is there a better fix?

Any ideas welcome!