Small Block Ford® 351W Four Piece Oil Pan Gasket With Fibrous Compound Rails. For All 351W Oil Pans Except: 11-660, 11-694, 15-670, 15-670S, 15-690, 15-694. NOTE: Our Ford One Piece & Four Piece Oil Pan Gaskets are NOT Interchangeable. The Ford® Oil Pan Stamping That Is Used With A Four Piece Oil Pan Gasket Is Different Than The Stamping That Is Used With The One Piece Oil Pan Gasket. The Four Corners Where The Oil Pan Turns Down To Go Around The Timing Cover Or The Rear Main Cap Are Sharper On The Four Piece Gasket Oil Pan Than The One Piece Style Oil Pan. For A proper Seal You MUST Use The Gasket Style That Is Appropriate For The Oil Pan You Are Using.