I think most of the forum parts vendors sell new date coded windshields. They are a few hundred bucks more but come with any date you want on them. Below is from Corvette Central.
https://www.corvettecentral.com/c3-6...%26count%3d144

 

 

I just bought one from Auto City in Isanti, MN. Evidently all these windshields are made in Japan and imported by Pilkington. Here is a pic of the inspection sticker. Check the thickness at 6.76 mm.. I suggest using a 3/8" rope instead of 5/16. Your stainless will fit better.

 

George
I bought a new WS for my 69 I believe from Pilkington in Columbus Ohio. I was lucky I could pick it up. I was looking for an original but gave up. I just put it in myself. I used 3/8 foam weatherstrip as a dam and the latest 3M adhesive to install it. Came out nice and the dam made the WS sit at the right height, no shimming needed.
joe

 

I replaced my 69 windshield in my garage this past winter. The original glass was .275" thick and the replacement glass was only .205". The factory damming strip is listed at 5/16" but with the thinner windshields you need a 3/8 strip or the windshield will sit too low resulting in a gap between the glass and stainless trim. The trim gaps came out perfect with the 3/8" strip.