The standardized windshield part number you're looking for is DW00587. I believe they are also available from other sources like LOF, and maybe even PPG. But they are all made in Mexico, and I suspect, probably the same plant in Mexico. Call around local, you may find it cheaper, and avoid shipping costs.
I did alot of shopping and research earlier this year, and when I could find a w'shield they were all right around the $400-$425 range. I finally stumbled across this guy on E Bay with a buy it now price of $345 and of course shipping added to that. Although he is in Oregon, I decided to call him anyway, and he was very helpful. I paid the price, and he arranged to have the glass shipped to the nearest Pilkington warehouse, (in my case Tampa) so I could pick it up myself and save the shipping charges. Nice guy to deal with. Bob at Bob's classic auto glass, Blachley, Oregon 1-800-624-2130, seven days a week.
He almost always has one listed on E Bay, you might want to do a search under 1960 Chevy truck to check his feedback, etc. HTH
edit: the curret ebay item number on his listing is 8002192611
