Airborne,
I just looked at the K8 wiring diagram and it looks like very little changed
According to this schematic
http://manuals.sohc4.net/cb750k/technical_reference/WD750K8.jpg The wire colors for what you need to tap into look to be the same as the K6 diagram I originally posted further up in this thread.
If you're going to do the relay mods, you should probably pop the headlight and look inside the shell and verify wire colors.
The 2 headlight relays, the Off-Run-Off relay, the Start button relay, and the horn relay all will go in there.
The only relay that goes somewhere else is the ignition Switch relay which goes under the left side cover near the rest of the electrical stuff.
Hope this helps.
Charlie
PS: If you need to talk this over, pm me and we can arrange that.