I've never really loved a fast rate hyd cam with higher rocker ratios.

If you had an air turbine on the motor to monitor air flow, there might be a clue there as to why the peak happened so early.

We dynoed a pump gas street 410 last year, rpm heads with mild clean up, small roller, 1 5/8-1 3/4 x 3 headers, victor, QF 850 carb........ Peak tq @ 4700, peak hp @ 5900, and only down 7hp from peak @6400.