Not quite sure what your on about here, the flow figures given has almost no relevance to a 300ci truck six, those engines are all modern engines unlike the Ford 300 which is ancient by comparison. If your aiming for 300 honest BHP, then you will need (superflow empirical data here) 300/6 50bhp per pot, and 50x4 cfm @ 28 inches test pressure, 200cfm. I doubt you will get that on a stock head, reworked with bigger valves and careful port work, maybe. The key is low restriction to flow (high cfm numbers) so anything you can do to help here is good. Spend your money on breathing. When you have good breathing you can use less cam duration to achieve your goal. Long duration high overlap cams have their drawbacks, (rough idle terrible fuel consumption) for street use you should aim for minimum duration that will get the rpm you want. In the case of the 300, its not going to be a big rever, so work to its advantage, low rpm torque, I would not use a cam over 220 degrees for a manual trans and even less for an auto. Aussiespeed have good 4 barrel manifold. The cast iron EFI exhausts look fairly good, headers would be slightly better, you will need a minimum of a single 2.5 exhaust and low restriction muffler. IMO this will give about 220 honest BHP which is pretty good for this engine (would be rated around 270). High compression isnt needed for this, if you have somewhere around 9:1 your good to go. Best advice, dont go overboard.