I'm not supercharged but I've been browsing on the subject a bit.

I think your best bet is to spend some time searching the www.mustangforums.com 5.0 forums. Tons of knowledge available once you sift through the fluff (like most forums that have been around a while). Here's an interesting recent post on choosing a supercharger:

http://www.mustangforums.com/m_945118/tm.htm

Basically boils down to: pass on the powerdynes, look at vortech and novitech, and maybe get a custom grind cam. It's a good read, some of the more knowledgeable guys chime in on it.

Every couple of days is a new question: what supercharger?

Hope this helps your research.