They are out there. If its just air to the front and rear you want haisley/scheid has one (7 runners, 1 for 1, 5 split and 1 for 6). If you want 12 runners for 12 intake valves, check out lazarsmith.com cummins 12-ir. The biggest issue would then be dividing the shared ports. would have to build material in the head and machine.