Classic/Antique Car Repair: 1966 Ford Mustang - Rear Main Seal, ford mustang, pcv system

Question
I have a 1966 Ford Mustang (Inline 6, original motor))and I believe it has a rear main seal leak.  How difficult is it to change and do you know if they came with a rope seal or a rubber seal?

Answer
Before looking at the rear main seal have you checked the PCV system to be sure that it is working correctly? I have seen PCV's plugged and not working allowing pressure to build in the crankcase and force oil out of the rear main. Let me know and we will go from there.
Brad