Well, with no specifications except "fits CB750 '69" there's no telling if it is going to require more power than your engine can generate, or mot. The Dyna uses more power than the 750 can make until 4000 RPM, so it is really relegated to hiway use only, lest you end up with a chronic low-battery problem. There's hundreds of examples of that in these forums.

Even the Dyna units with their 3-ohm coils have pulled so much amperage they melted the RUN-OFF switch on the right handlebars before, too: I've had to replace them and then tell their owners about it on several bikes. Those ain't cheap, and thru-handlebar wiring is a test of wills to install.