Early engine blocks have a groove in the rear main cap that holds the cork gasket.
This groove was eliminated in 72 in favor of the 3 nib design rubber gasket and matching oil pans. This design basically sucked and was replace in 76 with the "2nd" design 5 nib that suffered way less blowouts.
Unfortuately, GM still holds the patent on the 2nd design so all aftermarket oil pans are stuck using the 3 nub gasket.
2012 Mustang Boss 302 #1918, Competition Orange. FGF replacement 2006 Mustang V6 Pony, Vista Blue. Factory ordered. 2019 BMW X3 (Titled to the wife, but I'm always driving it for her. So I'm claiming it) Old projects, gone but not forgotten: 1967 FB 400, original CA car. After 22 years of work, trashed by the guy who was supposed to paint it. I had to sell it. 1980 Turbo Trans Am 1970 Mustang fastback, 351C 4Bbl, auto 1988 Mustang GT, 5 speed 1983 F-150 4x4, built 302 1994 Chevy K2500 HD 4x4, 454 TBI
