[750hp]

Any chance you can hit up the previous owner for the engine specs? That will give you a baseline to work from, but will also give an indication of stuff like what valve lash settings the cam is designed for.

Knowing the age and mileage of the motor might also indicate when it might be time to look at replacing/rebuilding things like roller lifters (if it has them).

I agree that 300 at the wheels is already a pretty healthy combo.