If he has enough time to really tune it in and try different spacers with larger carb sizes, I don't see why it shouldn't make 650 but it should make nearly 500ft/lbs torque depending on what LSA he has on that cam. 625-630 would be a safe bet on HP I guess. Very tough to guess without a complete rundown of what he has and all the specs. One thing's for sure, that old man... I mean Drag79stang will definitely like the way it runs compared to his old combo. Really should have a solid roller to get the most from that combo. Maybe he'll get one later in the year.