Sierra 18-1939 Riser Sierra replacement engine parts are designed to meet OEM specifications. Use with 3-1/2" I.D. exhaust hose.Material: Cast iron Ford Small Block V8 302-351 cu. in.; GM Small Block V8 305-350 cu. in.; GM Big Block V8 454 cu. in.; Interchangeable with: Barr; 20-0100; GLM; 56140; Mallory; 9-40113; Marine Power; 0992-593; Osco; 99204;