There is a 320 series that is worth avoiding. I think it the H series, but not sure. Also, you will need a sump that has the carb attachment in the middle of hte bottom surface. Many are horizontal, facing aft or on the botton very far aft. Neither of these will work with an A model.
RV-6A / IO-320, Flying as of 8/2015
RV-10 in progress