Best bet, get a service manual. You might have to get the electrical book too.
For a 1990 bike the electrics are in the same manual as the rest of the bike. Separate electrics books came along quite a while later, probably with EFI?
Sorry I haven't chimed in for a while. Had to pull the engine due to cracked crank case. I have removed the cb, and found dash panel. Still looking for a luggage rack and sissy bar. Thanks for all your info.