If you buy a supercharger, you're good for a "safe" 450 horsepower to the wheels which beats a 5.0's 444 to the crank. Then, if you want more power, which lets be honest, you will! Then you have to get your bottom end forged. This means forged h beam rods, forged pistons and a forged crankshaft. The parts for this will cost you another $2, 000 from mmr for a 5.0 stroker! That means you make your 4.6L 289 engine a 302 5.0L and it is supercharged and capable of up to 850-900 horsepower! (All depending on what forged kit you get)
Now, its not just this simple. Keep in mind you have to pay for installation fees as this is a very large job, a new fuel system to feel your new beast of an engine (gt500 fuel pumps, boost a pump, new bigger injectors, possible new fuel rails), you have to pay for new spark plugs (must change for just supercharge/turbo also), a new driveshaft to handle all the power (will need this preferably after 600 hp^trq), a tuner (you will need this no matter what!) And to pay for dyno time and custom dyno tunes (if you do it all at once, you save time and money, maybe the shop will give you a deal if they do installs also).
This is all to make a BULLETPROOF monster. After these mods, the car will go like crazy and keep hauling ***!
Final note of advice. DONT GO WITH ROUSH/EDELBROCK/VORTEC/PROCHARGER/PAXTON! This is just my personal preference, but centrifugal blowers are a waste of time and money in my opinion, if you want to go that route, go for a turbo! Much more power potential, better for the car and much easier to work with and to tune. If you are dead set on a supercharger, go with a twin screw. Now, I don't prefer roush because I feel like you're just paying for the name and logo with that blower and Its much uglier in my opinion. Kenne bell and whipple make the absolute BEST twin screw supercharsuperchargers out there! They have the highest power making potential, look much better, sound better and are just bad *** for the same amount of money! Why do you think the whipple is used on the ford gt?! Its a ford racing product ;p