Are you running the Chapman Stage VI heads on an RB block?, if so a Max Wedge port blower manifold should be the likely candidate, if you have the heads on a B motor, nothing available that I know of...I don't have my RB (440) blower manifold here for measurements, but I don't think there's enough meat around the ports to open them up to MW/Stage VI specs...Might want to try Indy to see if they have a blower manifold, I assume old-school 6-71/8-71?