Not to say years ago there could have been some sort of cobbled up kit to do that but I have been in this hobby since the early 60's and don't recall ever seeing such a kit. What you may be thinking of is a regular top kit for a sport coupe (which does not fold down) or a kit for a cabriolet. If you chop a coupe to try to make a roadster you will end up with a mess that nobody that knows anything about Model A's will want. Specifically, the value will drop out of sight. If you want a roadster, sell your coupe and buy a roadster. Or next best thing remove the coupe body and sell it and buy a repo roadster body.