Can a bolt gun in 10.75x68 be converted to 10.75x73 (404 Jeffery)?

Yours would not be the first. The magazine box will need to hold a .375 H&H length cartridge (3.5"). Then it is just a matter of rechambering and checking the rails for proper feeding.
I would highly recommend having this done by someone with experience, as well as checking the rifle for overall safety.

Hi
Yes it's possible to do soo. But why? I think the 10,75x68 is nice cartridge and rifles in that caliber is not common. The gun will loose a lot of value.

It's quite an operation to alter to 404 Jeffery. The feeding can be a problem to get 100% working. a 404 is really best suited in a 375 lenght action.

/JOHAN

What about conversion of a double rifle from 10.75x68 to 404 Jeffrery. Ku-dude