Question about rear chrome bumpers

[502ss]

I have an 84 1 ton crew cab dually that had this huge bumper on it. I have removed it and want to replace it with a nice chrome one. When I looked at places like brothers or lmc the pictures they have look like there is no backing where the license plate attaches. Did the bumpers from those years not have any material behind the plate? (I find that hard to believe). Can anyone shed some light on this? Here is a link to a bumper I am referring to.

Thanks
Jim

http://www.brotherstrucks.com/prodin...number=RRB91ST