The auto-oiler final output shaft changed in the K7/K8 with the 630 chain drive. Prior to that, the late K2-K6 output shafts were all the same, with dual-row final bearing. Before that, the output shaft had a longer shoulder and a 1-row bearing. If you use the shaft and bearing together, they will all interchange.
To use the 2-row bearing on the earlier shaft, you can cut back the shaft to fit the bearing (but I'd rather trade one with you, if you find one), and you must make a spacer to use the newer 2-row shaft with a 1-row bearing.
The 1-row bearing puts a bit more HP on the pavement, in the end. It will handle up to 90 HP at the shaft, which is about 105 HP at the crank, the 2-row even more. If you use the 2-row output bearing, check for a good inner bearing on that shaft, too. It's much smaller, and runs in dirty oil, so they tend to wear quite a bit, and generate and audible howl at around 30-40 MPH. Kawasaki sells this bearing for one of their bikes, while Honda doesn't carry it anymore. If you need it, I have the part # written somewhere in my notebooks, thanks to another SOHC4-er who found this for us.