There was a baffle, AMES part FN449KP. Basically a stainless steel plate. Not so much needed if you have correct gasket, most cars I've had went without. Carb sits on it, then it sits on gasket which sits on manifold. Serves to make sure the right passages are covered up or open. GM appears to have stopped using it after '67. If you are not sure you have the right gasket, then it comes in handy. Or else just get the right gasket (FN449KN). The harder thing with your swap will be getting the choke right (and perhaps linkage).