RMayer. personally I think a 750 is a bit large, youd probaly be better off with a 670CFM vac. sec. or a 700 mech. sec..
As far as your spacer, is it an open, or 4 hole ? With that set up witha 750cfm carb, I think youd be better off with a 4hole spacer,other than that I think Typhoon is on the right track.