Actually FE's are the only ones that install the plug being flat on the outside. That is how mine was leaking as well. I had to start the engine let it start dripping & then remove the bellhousing. That is when I saw the leak coming from the plug instead of the rear seal. Make sure that it is not the
oil pan or the intake leaking. The leak could also be coming from the hydraulic plugs as well.
I don't know the torque specs off the top of my head but it is covered in the "How to rebuild a Ford Big Block" book. A must book for all FE engine work. I want to say 85 - 90 ft/# but look it up to make sure