What is this called (Dash seal???) and do I really need it?

We have had the dash out of my son's '67 Dart convertible, my old '67 Dart hardtop, my '67 Barracuda convertible, and the '68 GTS convertible. Can't say that I have ever seen those. I would have removed them from the two '67 convertibles for paint and neither car had them. The Barracuda is a fairly late build, but the Dart convertible was Oct 27, 1966 SPD. The '67 Dart hardtop was a Nov 14, 1966 SPD. Yes, I have both fender tags on my desk...