5.9 Magnum Torque motor build?

Slightly disagree

First, live with the cam in there for now.
Second, a cam change, a very minor one, can still be a bigger cam and work from idle or slightly off idle and not effect any drivability or leave a gap in low rpm power.

Third
Look for long tube headers. Skip pipe max and building your own headers. It’s a crazy overkill suggestion for answering the pipe max equation.