Anyone know the flow numbers on a GM over the counter angle plug 292 head?

I got a friend running a set on on a 383 in a Chevy II Nova. He's running 10.90s using the cheap cast rotating assembly out of www.jegs.com and a Cam Motion solid roller cam .620/.620 252/257 106 and an old school torquer intake. 4.11 and 28" tire. Also a 2-speed glide and 3500 stall. All throttle No bottle. Just lite home porting, valve unshrouding. He's into the rev limiter 60+ feet from the traps at 7200 RPM. That car pulls so hard all the way through that when he chops the throttle the front falls 4-6". He's going to go to a 3.90 gear here shortly.

Anyway, I found a set fairly cheap but can't seem to find the port size or flow figures. They must be pretty decent though. That combo is working pretty good. He runs low 11s on a throttle stop barely cracking the rear barrels.