If those heads flow 300cfm +, then the cam is ill spec'd for the build imo based on the looks of hp and tq curve.
If the bottom end is what you've described, then it begs for a turbo. 500hp + 10 psi = need functioning seat belts lol.
I think that should be the long term goal adding a turbo or blower to it. I think that would make it the beast my dad envisioned it to be? That will not happen until I mini tub it and get a better tire under it. Meanwhile I will focus on getting it drivable and reliable.