It should have welded nuts on the inside of the door skin. If you pull off the interior door panel, you should see three there. If I'm remembering correctly. I finished my truck in 2012, so forgive me if that isn't correct.I recently (2 wks ago) bought a Custom 1957 Chevy Pickup. Problem is it didn't have exterior mirrors. So, I bought a set of original style mirrors. Is there a diagram anywhere of exactly where to drill the holes for both R/H & L/H mirrors?