Best 23 Degree Head that uses standard componets is the AFR 227's
They actually can be made better with some port work. I had Rons Porting port a set of the fully cnc'd from afr heads worth 2 tenths on my combo.
IMO The best head 23 degree is All Pro but if I remember correct it takes special stuff to use these heads.
http://www.allproheads.com/