I have a 55 Merc that I'm starting to work on.  I may end up using an AOD but need to leave the original tranny in for the time being.  Problem is that it hasn't been driven in many years and leaks like a sieve from the tailpiece seal.  Can that seal be replaced without taking the trans out of the car?

I also want to put a modern twin resevoir master cylinder on the car.  Anyone done so and have any suggestions/comments.