I agree with you Bob...
The 260 would be just fine, especially when it is what Matt wants. Let the gunsmith know what he wants and turn him loose. Nothing wrong with the cartridge on a pre-64 action doing what he wants with seating and then throating appropriately...
Back in the days when I needed to have a 257 AI or two, I had Ron Lampert put one together on a pre-64 that started life as a 30-06. It worked just fine. I would expect the same thing would hold true making a 260!!
It would be a fun rifle with pleasant recoil....
