TKM That rear main seal is a tough job to change...the real problem is you dont have a source for a quality seal. The originals were asbestos braid that is not available today. Do you have PCV or road draft tube positive crankcase ventilation might solve it. If you change be sure its vented or vacuum can suck the gaskets out of it. Also there is a tool kit to help that seal get in there ! Hope i'm telling you right its been 50 yrs. ! If not right someone will chime in .