For the gazillionth trans leakage thread...
Sure it's the pan? On my 727;(rarely driven as well) the converter leaks down and the fluid has to go somewhere. I swore my leak was the pan too. As the converter leaks down my leak was actually the threads of the front band adjustment stud
On the trans in my kids 72 c body wagon the leak ended up being the shift shaft seal
For all the world both looked like it was the pan gasket leaking.
Well we shall see as the 71 will be up on the lift in the next week to swap the pan. I'll inspect carefully and see what I find but the trans was recently rebuilt (last 500 miles) and new seals installed. Thx for the ideas!