window gasket questions

That white strip os the factory lock strip that has had the mylar covering wear off. It pushes the gasket outboard, locking it, hence the name lock strip. You can use a 70'-90 Chevy truck lock strip too, texture is different but only you and I will know.
http://www.classicindustries.com/truck/parts/pw1042.html look at bottom where it says "Also Fits":63-66 MOPAR!