I agree with Jim and also with the poster who said check your tire pressure. Sometimes it's the obvious things that are overlooked most often.
You didn't mention what springs you're running, but that would be my next area to look. Clamping the front half as mentioned above would help. If they are shot, buy the HD springs or SS if you are so inclined.
When you go to order you're Cal-tracs there's a form you have to fill out with all of your car's rear suspension specs. Make sure that you tell them about the inboard springs because it makes a difference in what kit they send you.
I'm gonna try and hook my Dart with the HD springs and 325/50 drag radials, but I'm running an automatic. If that doesn't work, I'll call Calvert. Good luck!