Most manufacturers figured out that riveting front drums to the hubs was a waste of time and money. As long as the drum is a snug fit onto the hub center, the wheel will hold the drum on tight enough without riveting it. The main concern will be runout, which shouldn't be a problem if there's a good fit on the hub. If you haven't removed the stubs of the rivets, leave them there to act as extra alignment dowels, even if you have to file them a little to allow the drums to slide over them.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!