You're right about the D/Dart as far as the factory goes. However, Chrysler put out a bulletin about retro-fitting the D-Dart goodies on 273 4 bbl models. No reason why the same thing could not have been done to any 273 4 bbl. If that is the case, the car should have a 750 cfm Holley, Doug's headers, and a 8 3/4 with 4.89:1 gears. The bulletin lists a Racecraft cam and other sources say it was made by Racer Brown. In either event, it would have a seriously lumpy idle.