Weiand #8007 intake on a 273 (Several questions)

A 750 is only 750 cfms at 1.5" Hg which is pretty restrictive but at .75" vacuum it flows more like 550 cfm. The carb rating has nothing to do with how much air and especially fuel your engine will use. When you tune your engine it will have the proper fuel to air ratio anyways. Not saying to go with the 750 but I can't see why it won't work. Carb choice has more to do with hp level than engine size since hp needs the same amount of fuel and air no matter engine size.