My guess is the super stock guy probably wasn't using those headers unless they made more power than anything else he has tried. I would try and make them work and report back.
69 Dart GTS A4 Silver All steel, flat factory hood, 3360race weight 418 BPE factory replacement headed stroker, 565 lift solid cam Best so far, 10.40 @127 1/4 1.41 best 60 foot 6.60 at 103.90 1/8