As far as I know,
Royal vacuums always used a double contact bulb. Later machines switched from 120V bulbs to 12V bulbs while still retaining 2 contacts. I don't think Royal ever used a single contact bulb. Kirby switched to 12V single contact bulbs with the introduction of the Classic Omega all the way to the Legend II.
DO NOT USE AN 1156 BULB IN A ROYAL!!!!
As for the wheels, best of luck with those ones from EcoVacuum. That guy is going to make a killing on those now that the originals have been discontinued. They're nothing more than roller skate wheels.