You will need more than just the heads. You will also need a 4 valve timing cover, a 4V timing chain and sprocket set, 4V headers (or exhaust manifolds), and a 4V intake manifold with all the components (throttle linkage, sensors, IMRC plates, etc). Also, once you have all that you will have to run a 4V ECU...so you will need one of those. You can use the 2V ECU but to do so you will need to get rid of the IMRC plates, knock sensors, and some other things. And you will need some tuning once all is said and done. The turbo set-up may have to be adjusted for fitment. All things considered, it probably won't be an easy swap. And at the end of the day you'll simply have a 4V conversion so it's not gonna make any more power than a stock 4V with the same set-up. In fact, your set-up will make a lot less power because the 4V heads have a larger combustion chamber and almost a flat top piston to keep compression adequate. Your 2V pistons have a larger piston dish because the combustion chamber is smaller. So doing the head swap will drop your compression ratio down to where the engine won't make any real power even with boost. You can get new pistons but then you're looking at a bottom end swap (and you might as well do the rods and crank while you're at it). Considering all the headache and money and downtime, you're better off just returning your GT to stock, selling it, buying a Cobra, and then fitting the turbo to the Cobra. You'll probably save a LOT more money as well as you'll have everything else the Cobra came with and a much more valuable car to boot. Or you can just buy an entire Cobra engine complete with ECU and intake and exhaust manifolds and then swap the whole thing out.
