Disc brake conversion wheel hub sizing

Ah, so thats what I was wonder about when I looked at scarebirds rotors, there are no hubs in them. So I would just re-use mine, which is fine by me except my drums are a miss match. One drum has the separate hub, when the other drum has the hub fixed to it. I looked on Rockauto and other part stores but don't see where I could purchase another hub, but have to believe they are out there. Maybe scarebird has some as well..
Thanks all for the replies! Maybe there is hope after all.

Scarebird isn't going to have the hubs. They recommend that you separate the drum
from the Hub and press in new studs.

Look at you hub/drum on the drum side, where the
studs come through. If they are still "swedged" together, that will need to be removed and the assembly will separate.

I've read using a 5/8 hole saw to cut the swedge.

I have scarebird brakes on the front of mine and it all works well together, just be sure to get quality calipers (Napa).