Originally Posted by Salamandrine

That's a pretty great unique paint job, and an awesome Mondia. I don't think I'd repaint either. The rust that was there at this point looks cosmetic. It cleaned up nicely.

For the main tubes where it is rusting a bit under the paint: I would try to treat it chemically with oxalic acid or evaporust. Then give it a few coats of good carnauba wax to protect the bare metal. The spots where the rust has started to peek through the chrome and paint are actually permanently damaged, but with wax you can slow it from reforming, though you'll need to clean it, de-rust, polish and rewax once a year or so.

PS a good source of oxalic acid is Barkeeper's Friend. It's cheap and it also works well on pots and pans.

IMO leave the steel crank. Swapping it for a 600 could easily be a big headache, swiss threads and all. I'd probably swap only the derailleurs, and install bar ends if that's what you like.