I have a Canadian 1981 CB750K. My factory speedo is in kph with mph in small letters. I know it goes well past 100 mph, and 145 mph sounds about right. Top speed should be around 125 mph. I thought only the SOHC's had speedos that topped out at 85 mph.
The wire wheels on the K models are standard. The C and F models cam with comstars (mags).
Where are you located? I think I recall seeing some Australian CB750 models with weird fairings coming in white but I could be mistaken.
1981 CB750K with 900 cams
90K KM's, rebuilt head, rebuilt carbs, upgraded valve stem seals
My wife's recipe website that I'm trying to help promote:
Strawberries for supper. Yes, I am a lucky man.