Big Block in a 67 Dart Convertible

My son's 67 convertible has a 440 backed by an 18-spline four speed and a 3.23SG 8-3/4 with ABSOLUTELY NO TRACTION HELP. He has sub-frame connectors and the body feels much stiffer than our 68 GTS convertible, but I still won't do anything to increase grip in a straight line, but the car does handle very well. I am doing the same thing to my 67 Barracuda convertible, but with a 727.