Based on the compression, cam and heads I'd say the rear wheel HP would be closer to 460 to 480. My all aluminum 496 FE with 10:7 compression, big solid roller, single plan intake, Quick Fuel 850 and Stage 3 heads made 681HP at the crank and 530HP at the wheels. We only ran it a couple times on the chassis dyno on a high humid day and still a bit rich so thinking it's probably got another 20 in it a bit leaner and better day but I doubt his combination would be over 500 at wheels. Pretty car however!
Here's pic of my KC 496 FE....
