Unless I am severely mistaken, Savage builds two action sizes in the 10/110 series. Short and long. The different numbers describe different metals, features, etc. Some single shots, some repeaters, different stocks, stainless vs. blued.
However, that said, there is nothing in the world longer than a Savage long action. The question becomes, how much longer than a 7mm magnum are you wanting to build? That's a question for you and your gunsmith. We currently seat bullets for my son's 7mag out longer than the SAAMI standards and have no problem with the magazine box. I have a buddy who built a .416 Rigby on the Savage long action, but I have no idea if he had to modify the magazine box.