Link for the parts diagram for the wipers: Windshield wiper arm interchange question
The nut is just a nut. If you have to cut it, you can probably take the pivot to a Fastenal and they can sell you a regular hex nut with the same thread pitch
Welcome! Those mud flaps pop up on ebay occasionally. I've even seen the ones that say "Diplomat" and "Volare" out there. If you look long enough you'll find a set.
Patience is everything with finding parts these days
The 360 Express is off a 78 to 79 Lil Red Express air cleaner. It looks like someone modified your original lean burn air cleaner and then dressed it up with the air cleaner lid off a Lil Red Expres pickup truck
https://www.performancecargraphics.com/Small_Decals/Air_Cleaner_Lid/360_Express.htm
That sounds like a dealership committed fraud well beyond a frame swap. Yes, you will absolutely go to jail if you frame swap a car, lie to you bank for a loan on that car, and then get caught.
Holy crap it sold
It was a classified ad, not an auction, so who knows what the final price was.
This level of ridiculousness reminds me of that 4dr /6 with a broken grille that went for $33,000 a couple years ago
https://bringatrailer.com/listing/1979-plymouth-volare-2/
30k is obscene...
Only for commercial vehicles would the DOT be involved.
This build is so old that probably already happened, if there even still is any VIN on the frame.
This is an antique vehicle. If the OP gets antique insurance, then even this might be not be an issue. If there is even a VIN on that...