Windshield replacement

I'm looking for advise on replacing the windshield on my 70 Duster.. I'm going to have a "professional" do it but I want to purchase whatever parts I need before hand.
I have a OEM windshield and I plan on getting a new gasket ($90 from year one).. One question I have is that the year one catalog has a "front windshield lock bead"... I have no idea what it is or if I need one..
Comments or recommendations would be appreciated...

Thanks