I don't know if you have done so already, but we should have a Factory Service manual for your bike on the home page of our forum. I'm pretty sure the location of the ring gaps are specified there. If not, I'm confident someone with a similar machine will pipe in with the right info.
Good luck, and I hope this helps.
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.