The front end is most definately a K2. K2s were the only ones to have chromed headlight ears which had the turn signals mount like the K0-K1 (K3 and on the signals mounted in a hole just aft the headlight mount). Also, K2s were the only ones to have the instruments mount like the K0-K1 (directly to the upper triple clamp) and have the warning light panel/handlebar clamp combo. K3 and on the instruments mounted to a bracket which was then mounted to the upper triple clamp. The painted brake caliper and the upper area of the lower fork casing are also suggestive of a K2. The light switch on the left handlebar is not for the US.
The frame is K0-K1 as it's missing the brake pedal stopper adjustment tab. The brake pedal though looks to be K2 or later (not too sure on this as my recently aquired K1's brake pedal also has a tab that should sit below the brake pedal stopper adjustment tab on a later K bike). The tailight, rear fender and rear turn signals are K0-K1; with the tailight being of the US variety. If the chain guard is plastic it's a K2; if steel then even later.
The sidecovers are K1-K2. Or, at least the "750Four" script is. The winged badge below the script will be red for a K1 and orange for K2 and on.
That's about what I can figure out so far.