The gibson site schematics show it both ways - the modern schematic
shows it going to the ground (the back of the tone pot), and the 1954 schematic
they have shows it between the vol & tone... I've wired them up both ways & never really noticed a difference in tone, so I imagine if there is one it's negligible.. one of the electronic gurus here (I'm looking at you Michiel!) may be able to shed more light.
Good luck with the modding