Overkill has a top mount system using a Magnuson TVS supercharger. You'd undoubtedly have to cut the hood for clearance but if you were up for that portion of the fab we could sell you the head unit and CNC water/air intercooler system. Depending how your Alfa's intake is set up we have a TVS 1900 system that points to the passenger's side or a TVS 2300 system that points to the driver's side. The lower plenum would need to be machined with LLT head ports which we'll be doing in about 2 months time but could step up that timeframe as needed.
This is our TVS 1900 system on the Colorado/Canyon 3.6.