Original GM20 (Flint, MI) Cast Iron Water Pump #3782608, date code F 25 8 (06/25/68) correct for 1968-70. Also fits 1963-67 Small Block Corvette, Chevelle and Camaro. Impeller Knob turns freely but unit in UNTESTED. Six slotted screws in place on underside impeller cover. Has been in dry workshop storage for 30+ years.