Backing Plates for 11x2-1/2 Brakes

I have 11 x 2-1/2 drums. Somebody in the past put a spacer under the drum. If I remove the spacer, the drum scrapes against the outer lip of the backing plate.
I believe, by reading other posts, that there are different backing plates and I must have the wrong ones. 2” maybe?
I would just leave it, but the wheels I want to use have 1/2” different offset, and I’m as close to the fender/quarter lip as I want to get.