[ll____b0t____ll]

You forgot the most important part for making H/P the heads .
what ya got?
Also you need to know what RPM the cam pulls in to match that with the intake .
And headers with 1 5/8 off into full 3" exhaust may net you a couple of H/P at top end but youll lose more torque on the bottom end.
Be carefull also of starving the moter for air and fuel by not using a stock fuel pump and not using a small air cleaner element.
Remember when dealing with heavy trucks torque woops horse powers butt all day .