I've installed both the rope style and rubber lip seal, both work equally well if done carefully.Yes, get a NOS rope , works better than the rubber seal if the crank area where the seal rides is worn or pitted.The rear seals in my trucks don't leak more than a drop now and then and it's maybe just the oily mess underneath created by the road draft tube.
It's always best to install the rope seal with the crankshaft removed like some mentioned above by Ralphy.But a satisfactory repair( leaks not too bad,lol.) can be accomplished by just drooping the crank slightly, which requires tranny removal.
