I have made that mistake once of replacing the early stock rope seal with the motor in the car, never again Mopar and probably others had a special tool for that, the bad part was you had to loosen or and remove most of the main caps which let the crankshaft weight hang on the timing chain while doing that job, not good
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)