1963 Dodge Dart Convertable windshield

Nope, same windshield on all '63-'66 A-bodies: NAGS number DW-625GBN. Try to avoid getting an XYG-branded glass (Chinese garbage).

The '63-'66 A-body "all except convertibles" windshield gasket is easily available from the likes of www.steelerubber.com . Go ahead and order it; it will fit and work fine -- this is confirmed by enough convertible owners to be reliable info. The difference is very slight, and it is cosmetic rather than functional: the convertible gasket has a slightly different contour at the upper edge and upper corners of the excess gasket material inside the car that overlaps the windshield header.

See also here for general where-to-get-it info for parts for your car.