For GM Block 8 Cylinder engines. Chris Craft, Crusader Marine, Mercruiser, OMC & Volvo 307, 327, 350. MC #'s 17437, 60658, 850399 Volvo #'s 885390, 856364, OMC #'s 985429, 980477, 3853850 Pleasurecraft # RA057018 Sierra #'s 18-3583, 18-3599 Fits Late Model Vortec GM V-6 & V-8 Engines Using A Composite Timing Cover.OE# 850399 1 Sierra# 18-3583