Recut the crown first on that 30-06 M70!. It may shoot even better.
I have all the cartridges I want after 60 years of it.
I have .358 Wins, 375's 38-55's etc.
The 30-06 is far more useful and all around than the larger bores for my hunting and target shooting.
It's marked 30-06 Springfield on a pre-64 M70 barrel is it not?
You can't do that over, where would a rebore be marked as to the cartridge?
Tweak the bedding then first. Then if necessary recut the crown first.
It strikes me that the man wants a 35 Whelen. Pre 64 model 70's are not sacred, especially in 30-06. They are all over and turning one into a 35 Whelen is no sin.
As far as marking the barrel you just stamp the new caliber on the barrel. In the case of my 35 Whelen, Cliff milled a small flat right over the original marking and stamped 35 Whelen there.
Like I said before the 30-06 is a good cartridge. But if he wants a 35 Whelen that's certainly one of the finest choices one could make in a cartridge.
No going back. Big deal. Pristine model 70 barrels are not too tough to come up with if he wanted to go back to original.