4pots1969 and kp,
In summary, and correct me if I'm wrong; in your opinion, if the guts of the engine are sandcast, then there could be some value there. Otherwise, the engine is an oddity but nothing special.
UK Pete,
I believe this is the path we will take.
All,
I'm probably 6 months away from starting this restoration, so I've got time to consider frame VINs, engine VINs, etc. We're collecting as much early CB750 parts as we can, with the hopes of having a '69 in our stable. We'll see what the next few months bring!
Thanks for your input,
Mike