The headlight bucket that's screwed to the car can take round or square lights, the pins which do the adjusting just get moved to accept round. Any 7" lamp will fit as they're universal, so a light from a early falcon or Datsun will fit, you will need the chrome ring and the ashtray looking bowl to locate and kept in line with a small tension spring .
I kept the squares on my van and added LED H4 bulbs so there's ways to get them to brighten the streets... Rounds do look way better tho 👍