2 basic ways to tackle the disc swap in the pre 1960 stovebolts.
Use a 5 lug camaro rotor/hub with a machined inner hat race. Of course this sets up the truck to be 5 lug.
Most of the 6 lug disc brakes use the original hub, but it is reccomended by the manufacturers to use the custom roller bearings and seals. The bearings and seals can often be found on sale for less than $100. The 6 lug kit claims it may not work with orginal wheels.
I have an ad drop axle for my 1940. I mocked the available 6 lug brake kit up on the axle to check for clearance of the artillery wheels I will be running. I had to grind a little from the iner spokes to clear the callipers.
Several people have done the conversion using stock wheels. Grinding on the calliper, rim, or use of a spacer, or a combination of grinding and spacer should accomplish your goal. Remember DO NOT GRIND ON A RIM WITH A TIRE ON IT. ADDING HEAT TO A RIM WITH A TIRE CAN CAUSE A DANGEROUS PYROLYSIS REACTION THAT COULD LEAD TO INJURY OR DEATH.
Here's a video showing why not to add heat to a rim.
