They used two windshields on all the C-bodies from '69-73. One fits the four door sedans and wagons (41,45,46) and the other fits everything else, two door sedans, two door hardtops, convertibles, fastback, four door hardtops, (21,23,27,29,43) Number refers to the roofline, second and third character in your VIN.
Of course, there are tinted and clear versions so they list four part numbers, two for each version.
You can double check this by downloading the parts manuals and checking part numbers.