Power brakes vs intake manifold 72 Demon
Welcome Jim!
Members "70aarcuda", "Rumblefish" and some others will know about that particlar intake better then i, but i believe you have a early M1 single plane. That casting # was on the same manifold used on regular lg. port heads as well as the W5 heads only the mounting holes were drilled wider for the W5. Those early intakes, if i recall, only had a small provision for a temp sensor and had no area drilled for a heater hose. I don't know about the gasket? That 2.50" number looks awfully big/tall to me.
As far as the Compcams "Magnum 270", i think the possibility of gaining a few more inches of vacuum for the brakes is there. Just make sure it gets degreed in properly. If it goes in set retarded at all you may have just done a cam swap for nothing.
One other thing.....This thread will get pushed back very quickly on this forum. It would do much better in the "Small Block Tech" forum. Maybe a Mod. will catch it and can move it......Good Luck, Rick