Alright so I figured this out. I JB welded the part back together and left it in. It helps direct air in the bi-level mode. That's pretty much it, if it breaks again it's coming out perminently.
Looking to see if anyone knew the function of part number 163 in the photo for the Air Ducting in my 1991 GMC Jimmy. It moves with the door which diverts the air to the floor/ defrost area. I just don't see a purpose for it and mine is cracked and does not function properly so I was...