Here's what I'm confused on. I've researched this in the past and found that any 235 after 1955 can use a rubber rear main seal. Anything before then must be machined to accept a rubber seal. However, it was my understanding that the '55 and up motors could use a rubber seal because no shim was involved. If I have to add a shim then I wonder if that means I'm no longer able to use a rubber seal.
Brandon
