I started to answer this morning, but decided to wait and see what develops with the answers. Not trying to be a naysayer, but you are building an intake that uses a 1 3/4" venturi going into what looks like over 2" diameter round tube. Unless you intend to install Dominators and spin it to very high rpms, I think you are way too big. Whatever your heads flow, whether a mild porting of 340 cfm, or radical at ~370 cfm, you only need a runner size for those intakes that is about 1 3/4" diameter at the head, and only slightly larger in the plenum for a small taper. You also will need to contour the opening into the ports quite a bit to prevent any turbulence and loss of flow. A smooth tube that is 1 3/4" diameter will flow over 400 cfm in case anyone is doubtful. We build things too large for optimum filling in my opinion. Otherwise, have fun, and keep us posted on the results after you get it running. Joe-JDC