Interesting that they're the 624/625 bars, that is standard-duty suspension with V8 engine. I would've been less surprised to find 626/627s or 628/629s (heavy-duty) on a 273-4bbl car.
Dan! Those seems to have been stock on the Dartchargers. All cars that I have checked has the standard suspension, standard transmission, even if they should have the 273x4 tranny and the standard shocks. My car had the standard shocks, standard rear springs, standard front torsion bars (dated 1964) and standard 273x3 transmission!!