Power brakes vs intake manifold 72 Demon

I have a 72 DEMON. I'm having problems stopping and the engine doesn't put out a lot of power until 3200 rpm and then its a rocket. I've been told to change the cam.
It has a mopar 4120231ac cam. (lift .484, dur 284, lobe sep 108, 2600 to 6000 rpm.
My engine guy sold me a Comp Cams 20-214-4. (lift .470, dur 278, lobe sep 110, 1800 to 5800 rpm. is this a good move?
I cannot find the intake gasket. the manifold casting number is P4452893. The port size is 2.500 x 1.125. It was running before, just not outstanding.
Help would be appreciated .
Also, where can I hook up the hoses for the heater?