Basically the Standard 110 Long actions will handle anything from 22-250 up through the 300WM class rounds with a magazine bolt head change depending on what you are set up for and what you want to shoot. If you want to shoot the H&H or RUM length cartridges then you either need to run it as a single shot, have it modified for the longer RUM Mag (since the RUM/H&H rounds use a longer magazine and the bottom of the action is milled to accept the longer mag), or get an actual factory setup for the H&H/RUM.

But yes the receiver itself is no different from the 30-06 version to the 300WM version. Just different Bolt Head, magazine, and follower, and those can all be switched pretty easily.

My advice is to pay the $15 and join up here. The Savage FAQ section (IIRC is paid members only, but check) has several pages of articles that answer questions such as this with detailed descriptions and photos to help.