YW
All my old cars (pre 1981) have VIN that are different than the current 17 digit ISO 3799 and ISO 4030.
There were zero issues registering these vehicles in Florida. FL requires a VIN and odometer validation for out-of-state vehicles using form 82040 by a Notary, Florida Compliance Inspector, Police Officer or Licensed Dealership. No idea on Illinois requirements.
IMO, the body rust shown in the OP is the biggest red flag and wouldn't work for me on a vehicle, but it seems like that isn't a problem for your project.
Good luck.
FWIW, I HATE dealing w/ that paperwork and agency stuff. They always seem to find a detail / obstacle to reject completion.