Read below, headers are not part of the program.
No head work needed except lift clearance. The retainer to seal should be checked and clearances made if need be. The 1.6 rocker ratio ... is it figured in with the lift mentioned? I see it sez roller cam. So, I'd like to assume it is a cam for the Magnum engine/head.
Porting wise. Leave the heads alone. Use the parts you listed and you will have what you want.
As far as exhaust goes, off the exhaust manifolds you'll be running, just do it simple. Dual exhaust with a X or H pipe @ no larger than 2-1/2. Mandrel bent if possible.