You might try www.bikebandit.com and look at their parts area. They have exploded drawings of everything for the bike. If they call out 4 of those o-rings, they usually indicate where they go.
Good luck on your restoration. Hopefully the postings here will help you complete it. Keep us informed.
Luke M
Used to have a 1979 CB750L, sold it as a parts bike, now riding a slightly modified 1984 VT700C. Network/Field Engineer. Central OH, USA, Earth, Sol System, Milky Way Galaxy, Universe.