My engine builder said they phased out rope seals by the late 60s and 70s. But I will do some more research on that. I hate to re-write history. ...so I will do some research.

The key here is avoiding the frustration of doing a rear main seal twice or more times is to find the answer to "why" it is leaking. Just replacing it with "something" may lead to frustration down the road.
I honestly would do some detective work. I know it is a pain with the engine in the car.
I'm not sure I would not just change everything and hope also.
But if you can look at the upper seal against the crank it may give you some clues.