i'm planning on using suzuki GSX-R throttle bodies. they're easy to get, cheap, and real nice. the 600 and 1000 have 42mm throats and the 750 and 1300 (hayabusa) have 45mm throats. only snag i can see right now is fueling, but they make bigger injectors for all of them, or supposedly honda 959 injectors flow much more fuel and drop in with a minor alteration.
edit: i just remembered another snag - the lack of a fuel return line on the GSX-R fuel rail. not sure how to fix that one yet....
we're talking 100-200 bucks for the assembly, including injectors. that picture is from an ebay auction that went for 70 bucks!!!!

it's too cheap to not do it this way.