According to this:
http://www.hondachopper.com/engine/engine_timeline/timeline.html the best answer most of us can give is "Yes". 69-70 were made until September of 70'. But if you're wondering if it's a sandcast 69' only the first 7k or so were sandcast. Still... you have the 23,573rd CB750K ever made, which is pretty damn cool.
FYI a lot of people call your engine the "K0" engine which is technically wrong. Yours is a CB750, before the K. K stands for Kairyou, which means "Improvement", and the K1 happened in 70-71. Good luck with your project.