The rope seal is OK if installed properly, which is not a simple task unless you have the tools as explained in the manual and if you've done a few before. Even then they seep a little oil.
Your best bet is the rubber seal.
The absolute best is have the block machined to take a modern pressed in single lip seal, but requires complete disassembly of the engine, a great thing to do with a rebuild. I don't have the link to an article about the conversion handy right now but some searching may turn it up.
