63 Valiant disc brake swap kits?

Replacing the studs should be no problem as long as the hole in the axle shaft hasn't been ruined. Even still, you can probably drill them and find an oversize stud shank that still has a 7/16 threaded section. IIRC, '63 didn't come with self adjusters, so, they've probably been added sometime in the car's life. They're a good idea though. Get a complete hardware set for a later model that came with the self adjusters. If it were me, I'd just order everything for a later model.....shoes, wheel cylinders, etc. I'd also go bonded instead of riveted, but, that's my personal choice.