Gears, throttle body, cams, headers, X-pipe, 24lb injectors and nitrous with a custom tune is all going to run you well into the $3,000 range....and that's assuming you're doing all the labour yourself. Count on at least another $1,500 in labour otherwise. Adds up, don't it? And the nitrous is a great equalizer....but as the old saying goes....it's only making power while the bottle is full.
Turbo set ups are not for stock 2V's IMO. Again, big expense, but small pay-off. Not to say the a turbo system isn't capable of making copious amounts of power, but you're limited to what your engine internals can take at that point.....which for the 2V modular engine is in and around the 375-425rwhp range. So unless you're prepared to spend another $2K building that short block, you'll be forced to run that turbo kit well below it's potential. That's a lot of money to spend, just to have to neuter the power adder in order to keep the engine alive.
A good off the shelf
Vortech supercharger will hit those numbers easily and will cost you about the same as your above aforementioned bolt ons, and about $2-3K less than most quality turbo kits.
Not to mention the Vortech is proven, has an excellent warranty and with it's use of a self contained head unit is a much easier and less time consuming install than any slew of bolt ons or turbo kit could ever be.
The best part about going with the forced induction route first, is that should you decide to do a few "little bolt ons" later on down the road, you'll be rewarded with much bigger power gains. Where a throttle body, mid pipe and cat back swap may have netted you 15-20hp when the car was still N/A, it'll net you closer to 30-35hp after the car is blown.
I can't stress how much I think bolt ons for this car are a complete waste of money. You gotta go with what works, not with what's become most popular because it either A) worked on other model Mustangs, or B) is a less expensive initial layout than dropping $4,000 in one shot. If you haven't got the money to burn, you should leave the car alone. If you can't resist spending money you don't have, you might as well hit up the bank for a loan and get it done and out of the way. At least that way, you'll establish a credit rating while you're paying off your parts.