New rotors, old hub...

Set the new "race" in the hub where you want it.
Get the old one, and put it on top of the new one.
Hammer on top of the old one until the new one seats properly in the hub.
Turn over the rotor, hub assembly, and get a punch, and punch out the old one.
Easy, peasy, if you don't have a bearing-race driver set.

FYI
ALL studs, either disc, or drum brake, are 7/16 diameter.