In 64 & 65 Chevy used casting # 3844461, being an Aluminum Hi-Rise manifold W/Holly Carb on their 327/350 H.P. Corvette, and Chevelle. My question is this; Does anyone know if this manifold was ever cast with an open plenum. I seen tons of split plenums with this casting #, but not an open. Just happens there is one for sale. Sellers states this is an original..never cut. Would appreciate any info that is available. Thanks