Jeff at MCH CNC ported a set of B1-BS I had to M.W. size They flowed 350 CFM at 700 on a Super Flow 600 bench at 28 inches, I put them on a 3.91 stroke 471 C.I. 440 bracket motor for a good customer in SO CA several years ago. The motor made 720 HP at 7000 RPM (it was still climbing but the customer wanted to stop the tests at 7000 RPM )on a cheap sheet metal fabricated tunnel ram and two Holley 750 D.P., KB forged piston with around 12.8 to 1 comp. ratio. Nothing exotic