The k1 was introduced part way through 1970 so if you have 1 throttle cable splitting into four cables going to each carb it's what you refer to as k0 (there really was no K model until the k1, it was simply a cb750) if it has 2 throttle cables coming off the handlebar going to a manifold in font of the carbs it's a k1. If my memory is correct all the 1970 models had the vented side covers and the 1971 k1's ( which I own) came out with the smooth side covers.