Engine Conversion

I've been looking to seriously increase the output of my car (2001 Z3 3.0). There are almost no superchargers and turborchargers on the market that I can find, but I have heard many people mention an engine conversion. Either switching the engine with an M3 or a 540i engine. Has anybody done this? Can you recommend a reputable shop that could do this? I live outside of San Francisco, so I would prefer a local shop but I'm willing to ship the car within the US.

What do you mean by no supercharger or turbocharger you can find?

If I can't fit a M5 V8 Engine, and even If I could I will be mounting this supercharger

http://www.vortechsuperchargers.com/products/units/j-trim.html

It works Up til 1100 HP with Adiabatic efficiency: 74% what means that
It's possible to run a engine at 814 HP with out loss in efficiency.

But it should be possible to fit a 3.2 M engine in your car, sorry but I don't know any shops in you area.

Still I believe the supercharger solution is the best or both.