Demo complete on thick walls, need to extend studs

Hello all,

I've finished the demo in a room. The room has two exterior walls. The exterior walls were 1 1/2 inches thick, comprised of lath, plaster and some sort of particle board/cardboard. A lot of material.

We are going to put up 1/2 inch drywall. So now our baseboards and window framing and door jambs are an inch too "long" (or our studs are an inch too "deep" I think the most sensible solution is to add extensions onto the studs so that they are 1/2 inch short of the window framing and door jambs, but I need advice from someone who has experience with this.

Thanks,
Tog