The idea was to compare the backing plates between yours and @FURYGT to see if you have the correct backing plate.Yes... there is about 1/16th of a difference. When I was looking, a few weeks ago, I couldn't find the measurements on sellers websites, so looks like have to buy and hope for the best.
Let me see if i can describe how I measured the drum. First measure the depth of the part of the drum where the backing plate fits into, the U-shaped part and I think it is about 1/2 inch deep. Then laid down the drum, backing plate side, or inside, facing down and measured the distance from ground to the inside of the drum, the side where the lug studs go, I believe it was about 3 15/16 on the good, original drum. So basically I measure straight down. Then subtracted the two measurements.
A quick summary of what happened. Looking at drivers brakes, noticed the drum had large crack from using torque wrench with the wrong lug stud. Bought a new drum. No problems at all. But then my Dad noticed the wheel hub assembly also cracked open on the stud hole. Hub had part number D70589 which turned out to be Wagner part number. Byron from ND, a great guy, had another D70589. I bought and installed it. My big mistake, threw out the broken hub before noticing the issue when I installed the 'new' hub. I wish I had the old/broken hub just to measure it and compare to the new one. I say 'new' because Wagner doesn't make this part anymore.
You want to figure out if the hub is right, compare it to the other side.
And.... I have to make a comment... Since I've calibrated thousands of torque wrenches (seriously), I'm a little taken back by "torque wrench with the wrong lug" comment. Don't ever use a torque wrench as a breaker bar. That's one of the best ways to ruin it..