Unless he's planning on 25+ psi and race gas or E85 I wouldn't bother with a 3.4. I wouldn't go above a 2.9 on pump gas. That's just me.
We can spend your money all day for you. But really you have to figure out your goals. If you're happy with 400-450hp I'd throw a blower on the GT and call it good. Pulley and tune the Cobra and leave them both alone. If you want 600+ then sell the GT as it sits and put the money into the Cobra. I built an 01 Cobra for 600hp. The money I put into that car I could've bought a low mileage 03/04 easily. It always seemed like it needed something else. Friend of mine just had a Whipple 2.3 installed on his 03 Cobra. It put down 587/555 on a stock engine with minimal supporting mods. That's on our 91 octane.
