Ur right about no access to freeze plug.... its been over 50 years since my last trans removal and somehow had memerious of seeing a freeze plug. It must been a automatic with its bell on it. With flywheel off i got second thoughts about coolant leak. I believe if the rear was leaking it'd be wet in the intersection corner of the bell and the block. Its hard packed dry sand there, not even wet with oil. Coolant is leaking forward of that inside corner dripping off pan lip and further traveling down to oil pan drain plug.

inside bell,dripping coolant & side of block photos. https://postimg.cc/gallery/2wxzb342u/