500 CFM mod

Years ago I built a Ford 250 cube inline 6 crossflow with alloy head, fitted a modified Holley 600 on it.....went like hell....had 275hp at the treads on pump fuel.
It was still pulling at 6,500rpm on the dyno, but the guy didn't want it to blow up on the dyno.
It was a 4sp manual with 2.92 LSD.