Okay now that it is available again I need to make a decision. I have a fresh rebuild with raised compression and a comp 252 cam. Original carb and distributer and mild porting. 1966 mustang original engine. How much power will this add to my motor? Of course a 2 or 4 barrel and headers will prob have to come also. If I change to headers now and a duraspark how much extra will this head get me?