Mild Magnum build

It sounds like the cam is where all the hopes of gains are coming from...and it also sounds like the one part of the build that contradicts your goal of a mild build.

FWIW, the Magnum 300 crate motor (300 crank hp) sounds like pretty much exactly what you have aside from the cam.
The Magnum 380 (380hp) crate motor had a hotter cam (no idea how it compares to yours) but it also had upgraded valve springs and a single plane manifold. It sounds like you're closer to the latter...so long as your valves aren't floating.

All I can say is that my 5.9 Magnum 300 (with the mild stock cam, dual plane manifold, headers, 650 carb, electric fans) is absolutely not impressive. At least it gulps gasoline like a real muscle car engine. :D I hope that cam wakes yours up!