Does a windshield from 1972 Plymouth valiant 4 door fit on 1969 dodge dart?

No, a 1972 Plymouth Valiant windshield will almost certainly not fit a 1969 Dodge Dart. While they are both Mopar products from a similar era, the body styles and therefore windshield dimensions are different enough to make them incompatible. Even within the same model year, slight variations could exist depending on trim level and body style (2-door vs 4-door).