Yea its stock but not a true 40/20/40. This is a split back bench. 40/20/40 in my sig is a future mod. Like the NBS Tahoes have, which is like bucket seats with a jumper in the middle.
Did our trucks ever come with a true 40/20/40?? Have you looked into fitting a NBS bench into your truck? I havent much good info on doing the swap