The early small block A/C set ups are very complicated (cast iron water pumps) . Everything must match to work properly . I believe you need a 4 groove crank pulley . 2 grooves drive the alternator A/C compressor, 1 drives the waterpump and one drives the power steering pump . The idler adjusts the water pump tension , the alternator adjusts the tension on the alt.,A/C and the power steering is adjusted at the pump . Note : you can't use non-A/C brackets on A/C cars and visa-versa except for the water pump pulley . Just won't fit AIRC
