In traveling the web for information about my Mustang, I've run across a lot of sites dedicated to improving the Crown Vic, Grand Marquis, T-Bird, etc. with the 4.6.
Here is one such site but I'm sure there are others...
You might try doing a Google search for something like "Grand Marquis supercharger" to find more.
http://www.mitchsplace.com/crownvicmuscle/index.html