A different bracket must be used if your alternator is mounted over the exhaust manifold towards the outside of the head. Due to alternator belt interference problem with base and adjusting arm.
Short water pump applications may require a 3 groove crank pulley.. MOST COMMON WERE 70-74 CAMARO & FIREBIRD, 70-74 NOVA, 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 CHEVY / GMC TRUCKS, 70 71 72 73 74 CHEVELLE / MALIBU / EL CAMINO, 70-74 MONTE CARLO, 65-79 IMPALA, CAPRICE, BEL AIR, ETC. But it will mount to most Chevy/GM engines with the correct mounting bracket. This pump uses the 5/8 keyed shaft for the pulley.