Have you made sure that the main seal is leaking and not something else?
I've seen more than one car have the rear main seal replaced several times when it wasn't leaking to start with
Does the flexplate or flywheel flange have oil slung out on the surface that faces forwards?
If not it is not the main seal leaking
The rear cam bearing plug or the rear oil galley plugs can leak and look a lot like a rear main seal leak
Good luck either way
I have loosen all five main caps with the engine and tranny in the car to replace the rear main seal on BB and early hemi motors, not sure if I have done that on a LA SB