Re: savage 110 rebarrel
Midway USA is also a great place for lots of Savage parts. Depending on the year of manufacture of your gun, when you get a bolt head to accept the Ultra, you may also need a new firing pin and cross pin.
When they started cranking out the big calibers, Savage switched to firing pin with a smaller diameter shank to use a smaller hole in the cross pin for additional strength. When I swapped a Striker from 7mm-08 to a .270x243WSSM, I needed the larger face bolt head, smaller shank firing pin (think it is .095") and the cross pin with smaller hole.
All easy parts to get and easy to swap. But I did have to reset the firing pin depth. The magnum bolt head is thicker front to back than the standard bolt heads and the stop on the pin would not let it move far enough to contact the primer. This may not be a problem if you buy a firing pin (w/ spring) for the Ultra...I was rigging a set up since parts are hard to get for the Striker handguns.