Are you sure you have a '69 Firebird rear license plate bracket and not a '69 Camaro? If you're using a Camaro bracket, then the plate will not be plumb. The bottom of the plate will be more forward as the op described. The '69 Firebird rear license plate bracket is a one year only part and (to my knowledge) not reproduced ….and they are very hard to find. The next time you go to a car show and see a '69 Firebird with a plumb license plate, ask the owner if you can take a look at the bracket.