65 Slant Six 904 leaking, causing slip

Over a period of a week or two sitting outside my 65 Valiant will lose about a quart of transmission fluid. The only thing I've done to the transmission since I've had the car for about 6 years is change the filter and adjust the parking and shift cable. It still shifts normal when it's full of fluid. But even with it pretty clean I can't tell exactly where the leak is coming from. It seems to be the shift cable area. I replaced the parking cover gasket with a new one when I reinstalled the cable. We just readjusted the shift cable to make sure it's going into gear crisp, now it is. So where's the most likely place for these to leak at? What do I need to fix it?