My state has a historic plate program that I was finally able to get into (there are limited # of license plate numbers that you can use to get a historic style license plate). It came in the mail this weekend and here is how it looks mounted. You can see the bracket is wider than the plate. The historic plate is only 9 1/2" wide, where a normal plate is over 12" Thoughts on what to do? Live with it? Take the bracket off and have it narrowed? That is...cut the ends of the bracket off and have them welded back on narrower? Something else? Example....Co40s seems to have a replacement bracket. Buy the replacement bracket and modify it. Keeping my original untouched.
In my opinion leave it alone. Altering an original bracket to fit a smaller plate is not a good idea. Let others also relish the fact that you have one of those limited "special" plates.
If being able to see the outside ends of the bracket bothers you, I suggest that you make a thin sheet metal plate that would go in between the back of the historic plate and the bracket. The thin plate would be slightly wider (and maybe slightly higher) than the historic plate and could be painted to match the truck lid.
In essence, you'd be creating a picture frame to go around the historic plate.
Cheers, Dean
Dean 'Rustoholic' Meltz old and ugly is beautiful!