Well this is one of those areas that you will find many different opinions. If I'm right the 268 series comp cam should be around .454 lift with 218deg duration at .050 lift. I would say that cam would be better matched to the performer manifold and not the performer RPM. The performer RPM is set up for cams that kick between 1,500 and 6,500 rpm's and also sacrifice some of your off idle torque. I would also guess around 650cfm's for a carb. Unless maybe your running a high gear-set in the rear and your engine is building rpm's real quick then maybe a little more carb. Just one opinion for an engine set up to deliver good off idle power/torque.
BUILT FORD TOUGH