This 7 Days to Die mod adds a slot for forge input. Works in single player and on servers. Three08 has changed the way he does this so it only effects the forges output slot instead of all the output slots. The download only includes the modded xmls for now, a SDX installer will be added later.
Just add the folder from the rar to yourgamefolder/Mods.
The forum topic of the mod is here.