Guess the HP

493 with std port SR’s, M1 single plane w/4500 adapter, 1050 carb, 11-ish CR, roller cam.

FW headers:
618tq@4100
639tq@4500

638hp@6100
616hp@6800

2-2 1/8 x 4 dyno headers:
518tq@4100
637tq@4800

673hp@6300
665hp@6800

The crossover point was 4700rpm.
Both were 567hp@4700, then the dyno headers just pulled away.
FW headers were 100tq better at 4100.