My advise on a hardtop is a complete NO NO, you'll end up getting a real funny contraption at the end of it. Unless you get hold of a very rare winter kit they came out for the M151s that had a hardtop instead of the canvas one.
You won't find that here.
This is how a hardtop looks. I know a guy in Indonesia who has an original hardtop MUTT.

Our local craftsmen are really skilled, you maybe able to get a replica made in glassfiber.