Billet Wheel adapter ?

Correct, with 1” thick adaptors you shouldn’t have any problems with the studs on the hub. Just remember that you’ll need an extra 1” of backspace to make up for the adapter

I'm interested with the set, but the vendor wrote me that he's not sure the adaptators will fit my '71 Demon.

What do you think about?

4PC 1" 5x100 To 5x114.3 Wheel Adapters 12x1.5 5x4.5 Spacers Changes Bolt Pattern | eBay