It is 1 1/2" total width wider than the CB750 tank then, so you will have to see if there is a way to extend the tube on the frame by 3/4" and reinstall the rubber donuts. I would get some thin plate, and a piece of tubing the same diameter and length as the ones on the frame, and tack them on the plates, and tack the plates on the existing tube mount for the donuts, and then install the rubber donuts on the new tube... am I making sense? Hopefully so. And, if you need to move the tank forward or back, up or down, on those mounts, it would be easy to do by adjusting the tube tacked onto those plates, by the size and location of the plates you will tack onto the existing tube.
Charlie