I can't say for sure, I'm sorry.
but I wouldn't worry about it. Although there were three changes, you can convert the earlier rope seal to the rubber item if you get it machined on a lath for small money.
A change from the stock rope seal to the later 302W style rubber seal somewhere in the 1970's, pssibly 1978.
Then to the more awfull 1984 XF item,
Then the lovely dog (ohc style) turd in 1987 .