Well if you really have the money(if you are thinking this you probably do) then what you can do is buy the long block, and the supercharger and do the following: upgrade all of the internals with maybe higher quality light weight components. Make it more efficient. Would allow for higher boost to be run on the blower and more power would be the result.Makes sense right? And after you are done throw that in to the engine bay and try to sell your current engine to cash out some of the investment.
If I had the money and time, I would do somthing like this, but then again thats me and the benefits may be very slight for the investment.