I used the ’74 Beetle wiper motor assembly on my Chevette MG TD. But I can see how one could modify the Chevette assy to work.
Not sure if they’d fit or not, but I bought my wiper arms and blades from MG Magic in Florida. (954) 680-2010 and ask for Brad Anderson. He is a straight shooter and will tell you if the stuff he has will fit to your wipers. Or he may have some options for you.
Sounds like you’re rebuilding a kit car much as I am. Mine has never yet been completed nor titled. So its up to me to get ‘er done! 🙂