If you have to pass California emissions tests, the only CARB approved way to boost a 3.0 is the Whipple supercharger kit. It's been discontinued for several years, and is pretty difficult to find at this point.
Of course you can try and get your own custom turbo or supercharger setup to pass emissions, but it may be much more expensive/time consuming and would probably require a good bit of trial and error.
If you don't have to worry about emissions tests, then it comes down to your budget, and how comfortable you are with custom fabrication. Morana v6 racing sells kits to bolt on either an M90 or M112. Their original design didn't work out well, but they've redone it since then. It's not a complete kit, but it's got the core stuff you'd need.
If you're comfortable with fabbing, and your budget allows a bit more room, a custom turbo setup would be way easier to get 15psi or more, and you could incorporate an intercooler much easier than with a supercharger.
