Everyone so far has talked about superchargers and i find them to be way too expensive and not be able to tune them much. I found a website that has a full bolt on "remote mounted" turbo kit for the hemi ram but say it fits the 4.7 too. The website is www.ststurbo.com
they claim that you can safely boost i believe its 4 or 5 psi on the stock mainfold. Well a stock motor period. Its a pretty cool kit for half the price of a supercharger kit. Plus it has the advantage of being able to boost it freely. As for feedback, there are lists and lists of reviews listed on there website. Let me know what you decide to do, im saving up for this kit myself.