For a Windshield, I would go with a new one. The biggest problem isn't buying one, but getting it shipped to you. I would start at your local Auto Glass Dealer. If that doesn't work, locate the closest aftermarket Vendor near you. But either way, be sure to compare prices.
Nice car BTW.
Keep us posted on it.
-Parting Out over 75 '58 to '73 Full Size Chevy Cars-
-National Impala Association
-Vintage Chevrolet Club of America