naddaclue, I don't thik you will find a after market replacement for that piece. You might be able to fab something up and weld it on, or find one at your local junk yard.
Your door shouldn't sag that much. That bullet shaped alignment pin should be centered in the piece on the door jam. A sagging door caused the wear you have experienced. The two pieces should slide together when you close the door with little or no rubbing.
If you can get your hands on a GMC manual for the 41-46 trucks, there is a section in there that tells you how to adjust the door. It involves putting a 2x4 in the hinge and closing the door on it, there by tweeking the hinge and adjusting the door up or down.
If you email me directly I can send you a copy I scanned.
George
