Duplicate "Fender Tag."

I would soak your tag in Evapo-rust. tag should clean up nicely
Did you speak to the guys at data tags?
It took me almost a year to get my one. the wait was with chrysler historical service to find my original build sheet on micro film.
They then sent a copy to data tags and then the tag was made. I also had to take heaps of photos and a pencil rubbing of the radiator support panel numbers and trunk numbers to prove the car was legit and understandably so.
Once all the info was with data tags, it only took them a couple of weeks to make it and send it to me. The quality is spot on.

It looks like your tag would clean up nice though.