Transmission Fluid

[Kisner]

How can I tell if I have too much transmission fluid in my 68 coupe (302, w/C4 auto transmission) without relying on the dipstick? The reason I ask such a stupid question is I have a repro dipstick which I don't think is the correct length. It's leaking around the pan and now a few other places which I'm guessing may be forcing its way out due to being overfilled. For example, when the transmission is cold, should the fluid be above where the pan meets the valve body? I know the fluid expands when hot. When I've changed gasket and filter in the past only about 1/16 of the dipstick sticks out of the valve body into the pan. I'm thinking it might should be longer and therefore I've got too much fluid in it.