What size Holley 4150 or similar for engine?

The street Demon is not the old BG Demon carbs which I agree sucked at best.This is the one I am talking about http://www.summitracing.com/parts/dem-1904 .
They are more like a TQ and are a spreadbore design that will work on a square bore intake.I am thinking of one for my 360.

The BIGS carbs are fantastic!Jesse modified an 850 dp for me and it ran awesome out of the box.I still have it and would highly recommend his services.