Really need some help, car pulling left and right

I posted a while back about my car pulling randomly to either left or right. I still can't figure it out. Since then I have swapped in a 360(which doesn't really have anything to do with the problem) and changed the ball joints and upper control arm bushings. I got it aligned and it still pulls randomly to either the left or right, i am at my wits end! Any ideas? thanks.