You're best guess please.

That cam is small for a blown 408.

With the nice heads it's probably 475 naturally aspirated.

Approx power level:

Boosted HP = NA HP x (boost pressure + atmospheric pressure)/atmospheric pressure.

475 x (10+14.7)/14.7 = 790 HP.

This is idealized so you have to factor in things like parasitic drag from the blower, the fact that roots blowers are pretty inefficient etc. it's probably a 650-700 HP deal.

Gonna be a riot to drive forrrr suuure!