I beleive that it would be fairly simple if you already have a turbo engine because the fuel system and intake can handle positive pressure (as long as you're not looking for very high boost low down).

You'ld most likely need to remove the A/C or P/S and install the supercharger in it's place but then the plumbing for any intercooler would be a little more difficult.

If you wanted to install an entire system the an older engine with the injector in the head would be better since then you don't have to keep any of the old system and you could install "fatter" injectors.

So far the biggest problem would be how to drive the compressor. If you weren't looking for much boost then you could take the easy way out and use a double pulley and run belts off the existing crankshaft but they'll wear very quickly. You'ld probably have to use a wide toothed belt which means changing the pulleys on everything you already have.

Just like everyone else, I'm going to say that it would be better to stick with a turbo........maybe a twin turbo like I've seen on TPC. But could I suggest going for the supercharger.......on a V8. That would be one hell of a car!