Just like the title asks, I searched around a little but couldn't find anything.

I'm gonna need a rebuild in the somewhat near future and need to know whether I need the 1" or 1.25" chain.

Your transfercase tag can tell you exactly what you got. It will say np231D D is for Dodge. It will have a HD if it is the HD (Heavy Duty) version.

It's an HD according to the glovebox. Good to know.