Yes of course it's "possible." The only things holding on a tank are two rubber grommets and one other point.
Possible doesn't mean that it will look good, proportioned well to the rest of the bike, positioned well, aesthetically appealing, etc. etc.
IMO it would look out of proportion to the rest of the bike, the tank would look very large. The cb750 tank will be made to hold more fuel, hence larger capacity, not just width, but length also.