On my 69 Cutlass S convertible. How does the vertical reveal molding connect to the drip rail? Seems like it takes some sort of thin screw and nut?

 

No separate washers used on the factory install....they just used #8 philips head screws with a wider head on them....that's why you're seeing the larger witness mark where the old screws were tightened down. Also....it's lower profile type head on the screw. Example pic below....