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.
Agreed......After a couple of pan gaskets, mine turned out to be the shift lever shaft (not the seal though). There was a small groove actually worn into the shift lever shaft and it took 2 seals to figure that out because the groove was so small.