Could you measure the thickness of your new one compared to the old one. I wonder if they are a little lighter. I'm wondering how the AMD stuff compares to the cheap line of glass installation shop glass.
Factory 68 Super Stock cars ran lightweight glass. I love to shed some high weight.
FWIW there was someone selling 67-72 Dart side glass from Brazil that was thinner than factory. Not marketed like that. But a inexpensive way to get some S/S glass.