Uh, I'm very capable of doing the kind of rethreading work in these situations but I try to avoid it as much as possible. I would just replace the cover with one out of the junkyard. The way your luck has been lately, you're better off just replacing things instead of fixing them. You don't need to try and fix these kind of mistakes others have caused by working on your car. In my experience that just makes things much much worse.
Model 35, right? Should be on just about every Cherokee, Comanche, Pioneer, Concord and late Hornet in the picking yards. Maybe a Wrangler if you actually have that kind of luck. Might want to bring the defunct cover or a diagram to match. O_o
I've never had to undo the cover plate before but I'm assuming they have a gasket. I'm betting you'll need a new one as I'm guessing the cover hasn't been off of there in over 30 years.