Where can you find a bolt diagram for a Churchill Highlander by Kassnar chambered in 30-06?

That is a tough question. Those very nice little rifles were made in Italy by Fabrique Italiani Armi Sabatti, and imported by Kassnar. Kassnar went out of business, and Mr. Kassnar became the head of Charles Daly Firearms, which THEN went out of business. You might contact the original maker through their website in Italy. Absent that, I do not think there IS a source for a parts diagram. Your rifle is between 35-40 years old. Sorry-