I did a 440 about 6 years ago, moderate cam, headers, and an 850 cfm on a dual plane. One of my employees had Desk Top Dyno and ran the specs. Came up with something around 430 hp. Great braggin' numbers but I think a bit optomistic. Never did a real dyno, so I couldn't disprove it, but I never really believed it either. Since it wasn't my program, and I didn't run it personally, there may have been some adjustment factors that the guy didn't enter, but he loved doing it so should have known all the steps.