A 1970 CB750 could be a very valuable bike, no matter the condition. Get pics of the frame AND engine numbers.
If they are not "matching", value goes way down.
And FYI - the numbers will not be identical, it most likely came from the factory a couple hundred numbers off. It could have a later model motor, we can look up the year from the number.
Or, it could be blank if the motor was replaced by a dealer, fairly common.
Good luck!