There's a couple different superchargers that work nicely with the 4.0L v6. If max power is your main focus, than a centrifugal supercharger is a most. Your best bet for max power would be the Procharger stage II kit
. It comes with the a 2 core intercooler, 39lb injectors, computer programer, and other odds and ends for a complete install.
The only thing you may need is a fuel pump booster or an upgraded fuel pump. Other than that, you'll very very close to your 350hp goal at 10psi. This is also assuming your Mustang is mostly stock?
I should also mention, with this much power you're going to quickly find all the weakest links in your drivetrain. Especially the factory rear. I highly recommend switching to the 8.8 rear found in the GT's. Although, maybe you already have some upgrades? Fill me in on your current mods and budget and we can go from there!