Hola For many many years the power steering pump was of one design/style. The only differance was the setting of the pressure. Imperials had a higher pressure setting than Chrylers ( the pump in the hand looked the same ). Then came 1967 and the 375 hp engines ( we only speak big-block here ). The pump pulley was a spoked unit with a larger diam than the standard unit. The pump assy and the reservoir was still the same make. Then MoPar went to the Sagnaw units. The Sagnaw units have a narrow body and some of them also have the spoked pulley. And some time an other MoPar went back to the same pump units that was used only on the hp enginges with large diam pulley's. Since the large pulley eats less power than a smaller diam pulley this unit was used to try to regain lost hp from the lower compression ratio's and softer cam'd engines. It was about at the same time that MoPar started using the fresh air hose to gain hp from the free ram effect of the hose ( see Olds 442 starting w/196? ). When MoPar went back to the larg diam pulley's the dual snorkle air cleaner housing had already been put to rest. But, the exhaust manifolds were still beening explored. Rodger & Gabby