Need help identifying drums 5 on 4.5" size 11-2.75

Hey all, new here.
I have a tandem axle car trailer that has 11" drum brakes and cannot identify them. They have adjuster holes in the drum, and take a 473PG raybestos shoe, and a H7046 spring kit. The backing plate bolts to the trailer with 3 bolts, 1 at the top that also holds the top of the shoe, and 2 that are 2/3 of the way down the backing plate. This leads me to believe they are off a car...they are not chev pick-up drums, but very close. 2083 raybestos does not fit. They look like big dodge or chrysler brakes....I have spent hours searching, and at the auto parts counter...any help appreciated.