Ed, on my '51, there were holes in the reinforcement under the cowl. I just used those to locate the holes in the cowl. The repop right side mirror bracket has just two holes like the original left side bracket, but the bends in it locate the mirror head forward so it's visible through the windshield instead of the side window.
Hard to tell, but your truck may be a Task Force 55.2 series. The nut plate is a good idea.
