The knuckles are different but the spindles are the same. That was the trick behind the Viper 11.75 that I used to make. The 11.75 rotor fits on the drum brake spindle and the mounting bracket bolted to the drum brake knuckle pattern. That kit worked pretty well back in the day.
Here is a picture of a '73 drum knuckle with the Viper caliper. A 11.75 rotor slides right on the drum brake spindle. This was a super low cost way to get a pair of high quality calipers onto the front of a Mopar. I stopped making these brackets but DoctorDiff can set you up with something similar.