1958 - 1965 Chevrolet Late 348, 409 CID Rubber Rear Main Seal Best Gasket 3610X from BOP Engineering. Fits all 348 and 409 except early 1958 348s. This is the highest quality seal available for this application. We have specialized in rear main seals for over 25 years and have a reputation second to none in service and quality. Buy with confidence.