10" rear backing plates??

Are the 10: rear backing plates the same for the 1 3/4" drums/shoes as the 2 1/2" drums/shoes? I am assuming that since the Abody 8 3/4 only came with the small bolt pattern and the 1 3/4" brakes, that the backing plates I will need to use to install the larger axles and the 2 1/2" brakes will need to come from another model car?? I just bought a pair from a member here, and the first thing I noticed was that they only have 1 adjuster spoon hole rather than 2 and they seem to have no raised areas for the shoes to rest against? Does anybody have a picture of the what the correct backing plate would look like to change over from the small 1 3/4 brakes to the 2 1/2" brakes and the larger axle pattern? Thanks.....