Instability Question

I recently replaced all suspension components on my 71 Duster and got a front end alignment from a reputable shop in the area. I have a serious issue. Whenever I hit a rise in the road, go over a bump or a bridge the car gets real unstable and wants to veer to the right ditch! It is very dangerous and with the 440 Super Commando very fast making it very deadly. What could be causing this instability? Thanks for any knowledge on this issue.