cams on a 4 valve are really one of the worst bang for the buck options. its more of a sound mod usually. do you really not want to supercharge it? you could easily make 400 at the wheels with just a supercharger. ive got a friend w/ a mach 1 w/ an f1a and meth injection and he's way past 400. the only thing is you will need a good tune/less boost due to the higher compression of the mach compared to a cobra. i would say just go w/ the blower, it alone would put you over 400 w/o going into the motor. and its cheaper than getting cams + bolt ons to do it n/a.