Locke

I'm not sure if this is the right place to ask, but here goes. I've looked at several 240z's locally that were '73 models, produced in late 72 and 73, and every single one of them has had what appears to me to be round top carbs. I've read online that 73 was the model year that the carbs went to the horrible flat tops, but since all of the ones I've seen haven't had them, its hard to believe that all the previous owners swapped them out for their round counterparts. So, is it possible that these 73's came with the round tops either stock or as a dealer option, or were they all aftermarket mods?