72 Dart 4-Door Windshield Gaskets

Yep, it's true, you do need those gaskets. And they need to be installed with an appropriate type and grade of sealant goop, which is called 3M Glazing and Bedding Compound -- see this thread. The sedan gaskets are different from the 2-door hardtop (Swinger) gaskets, and quality really matters. I'm getting mine (for my '73 Dart Custom 4-door; same gaskets as your '72) from Steele.