Hmmm, In a word...............Complications. You would have change alot of things besides just the supercharger.
Check this site:
http://www.bonnevilleclub.com/forum/
I have a 2000 Grand Prix GTP (same engine as the SSEi). Its not really the same as the naturally aspirated 3.8 engines. 205 vs. 240 HP.
Compression ratio is different, computer has different programming, trans is the HD type, ect..
I guess it COULD be done but would be very expensive.
Check out the Bonneville website and see what it all would entail. Also check out
http://www.clubgp.com/forum/
Good Luck!