Supercharger for a 2007 Pontiac Grand Prix base model (3.8 L26)

If it was my car, I would not reccommend adding a turbo/super charger without strengthening the internal components inside the engine as I believe the supercharged engine from the factory has stronger internal parts. Typically to do a significant modification and to get the most out of it would usually require upgrading other components, i.e. higher flow injector, reprogrammed PCM, exhaust and possibly so on.

What you want to do is a top swap. You'll need several parts from the L32 motor, including throttle body, lower intake manifold, cylinder heads, fuel rail w/ injectors, valvecovers front and rear, harmonic balancer, idler pullies, brackets, tensioner, etc