The B and E body HP manifolds can make 475hp or so easy, beyond that, you'll be giving a lot up to pumping losses compared to a set of cheapie headers. Also ,the more power you make with them, the more important the camshaft becomes. With your build, I would do a few things. First. Sell those 413 heads. If they arent Max Wedge, they are an old, small, flat port design, and the closed chamber wont do any good making 9.5:1. If they are Max Wedge, you can finance your build with their sale, because the ports are too large for your intended use. Use the open chamber 452 castings. I'd keep the stock valve sizes, but do some bowl cleanup, and have a 5 angle cutter valve job done. KB237 hyper pistons, and a steel shim gasket should get you your 9.5:1. FOr a cam, get a split pattern, more exhaust duration and lift, and a centerline in the 112-114 range. Most modern fast rate cams have specs like that, so you can "choose your poison" so to speak.
