I am retired at this point but, back in the day when I made a cyl head have better flow #'s ,99% of the time the car was faster, this has worked for me since the 80's, also the HP increase showed up on our old Gopower Dyno, I will say technology has passed me up but what I have done in the past has kicked butt on the track.

1968 Charger COLD A/C Hilborn EFI
512ci 9.7 compression, Stealth heads, 4.10 gear A518 ODtrans 4100lb,10.93 full street car trim
2020 T/A 392 Stock 11.79 @ 114.5