@Brooks James No, no. The calculator wanted the measured depression that the heads were flowed at . Typical through the industry is 28".
If you run the calculator again, you will get a little over 400 hp.
At 14.7 atmospheric pressure those heads probably flow about 100cfm.
Edit : if you run that calculator at 28", and 185 cfm to account for the intake manifold, you get a realistic 351 hp. Add 150 shot and voila! 500hp.
