This manifold is a direct replacement for the stock manifold on 1972-?86 GM Small Block Chevys with EGR and 1981-?86 GM Corporate 350 V8 engines with EGR. It is essentially the same design as the 52000/52001 except it incorporates a provision for EGR. This manifold is an ideal street manifold and provides street legal operation in the listed applications as well as improved power over a wide rpm range. Will accept late-model choke, waterneck, air-conditioning, alternator, and H.E.I. ignitions systems. This is a great all around street performance intake manifold.