This link my help you.
Kadey-Krogen Yachts: History
As far as I can tell K.K. never made a 75' vessel. (But I may be wrong on that.) All the sites I have been to there is nothing about a K.K. 75', but that does not mean they did not build a one time costum job for someone.
There has to be some kind of paper work with the vessel that will tell you the Hull # and who made it and also the size of the vessel. Once you find out the builder and the hull # you can contact that company and get all the info on the vessel they have on it.
In any case. It does look like a nice vessel and with a little hard work she could be a great vessel from the looks of it.
All the best to you and happy cruising to you.
Oh. if you do find out anything about the vessel, let us know about it