DickH, I ‘m assuming you are referring to upgrading to a progressive two barrel carb since some Chevettes used them. It would require changing the intake manifold since the one barrel manifold carb mounting surfaces would not match up with the larger two barrel carb. I do not know of any one barrel carbs for upgrade purposes but I’m no expert on the subject. Rick Drake , on the Chevette forum , can point you in the right direction . ray10’s link above will get you in touch with him.