They sure aren't easy to find in decent shape. And interestingly enough, there's two styles of them. One has longitudal lines in it and one is a pebble style gutter.
I lucked out this year when I parted out a pair of 66 full size wagons and one of them had a gutter in very decent shape. I needed it because my Grande Parisienne had nothing left of the original gutter.
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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars (now converted to a "factory" 4 speed)