Yup, WSM calibers are large shank, except for the first production runs. A few RUM and WSM rifles were built on the standard shank. Standard shank barrel nut is indeed 5/8 long.
I have a 1990s model 110 savage 3006 rifle. I want to replace the barrel with a heavy flutted and threaded barrel but I don’t know what size shank it has. How do I determined whether the shank is large or small?