The SOHC bikes came from the factory with a D.I.D. 530 standard chain. On my '81 XS400H, I use the DID 530S Standard Chain – D18-531-110 with 102 links which is what the service manual calls for. O-ring and X-ring chains sound like a great idea, but are wider than the standard chain and will rub hard parts on the bike. The D.I.D. chain is about 50 bucks, so won't break the bank. If you must have an O-ring chain, I understand that the RK 530UWR (sealed, but narrower to fit like a standard chain) might work, but I haven't tried one.
In looking at the DOHC manual, it appears that those bikes use the same chain and number of links as the SOHC bikes, but since I don't have one of those models, I can't say for sure.