Animal is correct. You need to rob the fuel system also although if you look at the big picture compared to what you will need to spend it's a small cost.
If you own both now???? You don't need to think about the difference between the two as far as power, and potential.
If money grows on trees in your neck of the woods you will always be able to build more power with the Cobra motor, you know that. I saw an 03 anniversary Cobra the other day at my dyno making almost 700 rwhp! That was with a Whipple, KB boost a pump and tune of course. I know it was the real deal because my dyno guy is more conservative than Pat Robertson.
Anyway, if a Saleen is what you want, then stick with that and build the bottom end. You can make 500 rwhp all day as a driver with the series V if you have the tune on a forged bottom end. I know "E" cars that are making close to that. Also, remember, if you start hacking up your Saleen you kill the resale that would hold a lot better than the Cobra in the long run.
When you said "600" hp before did you mean rear wheel? If not then you will save a ton of money keeping your Saleen and builging that motor and topping it with a good twin screw.
If you want your 600+ rear wheel hp you would be better off driving your Cobra and selling the Saleen and holding out for a Saleen/Cobra. Just my opinion.
Forget about the "Cammer" 14K and you need to keep your Saleen motor for emmissions unless youre in a lucky state. I do like that it's a stand alone set up though.
Good luck.