Never I good idea to compare data from different dynos...... But.....

416, 12:1, port matched SV, old school 850 Holley, we have a couple sets of dyno headers for these things, and to the best of my recollection I used the 1 7/8 x 3.5 on this motor.
Flat tappet cam, old school .842 lobes, 265/270-106 in at 102, .375/.375, crane 1.5 ductile rockers, straight c12 gas, timing 36, lash .022/.022.
RPM heads with some mid-level effort porting, around 270cfm.

539 uncorrected hp.
Baro 29.98, .53 vapor pressure, 78deg air temp.
BSFC in the low/mid- 4's until the last 4 lines, where it went up to .48-.49.

2.02 valve, 4.00 bore:
Lift-----flow
.100---65.4
.200--132.9
.300--190.3
.400--234.3
.500--268.3
.550--277.8
.600--269.1
.650--268.3