You don't want to put the TBI on the magnum intake. The magnum intake is designed for dry flow only and putting a TBI on top will give you an engine that runs like a bag of crap. You could put a propane mixer on there, because it's a gaseous fuel.
What about aftermarket intakes? Any real benefit to putting something like the AirGap on there and fitting the TBI to it? Does an adapter to do this exist?