Horsepower shmorsepower, This is what mine made
I have ran the 556" combo myself with similar results that your friend had Beast477. As a comparison of power, my 582"tall deck,12 degree Profiler headed, cast ported profiler intake with near 15 1/2 to 1 comp using a 6 cc dished piston ( due to the small comb chamber) and Jesel 1.75 ratio rockers and .922" lift at the valve with Pac #1349 springs with 1064# on the nose and 375# on the seat requiring 7/16" push rods. I run a single 1400cfm Dominator on gasoline that makes 1170 uncorrected HP at 7450 RPM and 924 # torque from 5600 RPM to 7100+ rpm. Steve Schmidt & company ported the heads and gave me the valve train combo ( I would have never arrived at this answer on my own or budget) a few years ago. We run real fast with our TH 400 trans with a 2.10 first gear ratio. The stock 400 2.41 ratio is too much ratio at this power level on the starting line to hook it up easily.
Bruce