Disc brake conversion wheel hub sizing

Unless it gets damaged in some way, I'm not sure it ever go bad. The bearings and races are replaceable and are available.
Hub failures are bearing spinning inside the hub ruining the bore or lug stud spinning in the hole. Dorman did offer these 7/16 studs with oversized splines so a spinning stud was repairable. I don't know if still available. Scarebird requires longer studs anyway. I don't know if those will be 7/16 or 1/2 and I don't know if your wheels accept 1/2 inch studs. 1/2 inch lug nut will require a different lug wrench.
Good used hubs for the 9 inch or the 10 inch drum assemblies are usually found through "parts wanted" here.