It would probably have to be a Model 70 in a magnum action. But I don't know what magnum caliber would allow a rechamber to 264 Win Mag, so I am at a loss here. You would most likely have to get a Winchester Magnum action and have it rebarrelled. That would certainly be less costly than a new rifle.
If it is definately the 264 Win Mag you want and not another 6.5mm bore with similar performance, a rebarrel is all I can think of (but I'm limited here, lol). If you have a non-magnum M70 in 06 hanging around you could always have that rebarrelled to 6.5-06. Just a thought. Mikey.