:)thanks everyone.
I will go with HYBRID. The tank and side covers were re painted in the US and the colour although slightly light is a factory colour from what I know.the tank is new and a K5 as the petcock is on the left side.
The Owners Manual which came with the bike is printed in1972 and is for a K3. The seller in the US reliably informed me that the bike was a one family owned bike and as its only travelled 20570 miles and the condition generally I believe that to be true.
The frame and engine numbers suggest K2 but the switches and clusters etc are standard K3. The bike was built in July 1972 so I think it is a late K2 with K3 equipment from new.
From a resto point of view I think that's what I need to do.
Thanks for all the advice ...it's really appreciated.
I just want to get another good 750 back out there as close to spec as I can.
Thanks again 
There may be the clue: the model years (aka "K" models) ran from July through June of the next year, until the K3 came along. After that, it was judged by the K model only. Your picture shows a K3 seat and front disk setup. The K2 came in the Garnet Brown, and a very few K3 that I have heard about as well. Honda could not give that color away, in the day! It was a Valley Green laid over the Red Candy Metallic colors. I had that very color (it is still lurking under the present gold) and it became red where the tank bag wore through the green, and yellow on the sides where the sun faded the green. It didn't wear well, getting to this stage in just 3 years.
