I have read a lot of the posts on rear main seal fixes on this site and I have replaced the rear main seal twice. I still have some leaks. I have used the rubber seal both times and I am beginning to believe that I may have one of the early blocks that was not machined with close enough tolerances to accept the rubber seal. As I look at the rear main cap with the seal in it, it looks like the lip is not sticking up enough to get a good seal. I have heard mention of shim material to move the lip up higher. Does anyone know how high the seal should stick above the main cap? What shim material is best to accomplish this? I would like to stick with the rubber seal if possible due to ease of installation. If there is not a way to make the rubber seal work, I have a set of rope seals and will try them next.