OK
@Troub from what I am seeing on the top picture of you fitting the cowl everything looks good except where the cowl meets up with the A Pillar like you are saying. I had 12 years in the autobody trade as a young man.
From what I am seeing here and understanding how these cars were probably assembled going down the assembly line. I would say that the cowl panel was installed and spot welded in first, then as they went down the assembly line the outer skin of the windshield A Pillar was installed on top of the cowl over lapping on top of the cowl.
You see that step down edge on the end of the cowl, that is the area that the next panel the windshield pillar outer skin drops on top and lays in that drop down lip. Then after the final touch up grinding you just lay some filler in there to bridge the 2 parts level and even. So yeah I would say you need to slip the cowl under the windshield pillar skins.
Here are a couple of pictures of a 1967 Dart 2 Door Post car at the cowl to the windshield post area. Hope this helps . . .
Not sure what your 2nd photo is showing, unless it is from underneath looking up ??
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