Hi,
For what it's worth, on my 76K:
1) ignition key is mounted right between the gauges, meaning, not under the tank
2) your petcock looks like the "earlier" style
I think both thoses changes started with the 75 Ks.
Also, didn't pay attention to the speedometer on the picture, but another way of telling (if they are the stock ones, of course):
74s had an increment of 20 (e.g.: 20, 40, 60...)
Starting with the 75s, the increment was of 10 (e.g.: 10, 20, 30...)
Paul