Rich-
Where is the leak? All of us are quick to assume the front seal has failed
in an old car but that may not be the case. I solved my 73's problem by
replacing a $4.00 selector shaft seal.
If you can, put the car up on stands and spend some time inspecting the
trans. Remove the torque converter cover and look inside the housing for
dripping fluid to confirm a front seal.
Good luck.
Phil Brust
73 & 82 Imperial