If both tires are cupping on the inside and you've already replaced the front shocks, and the control arm bushings are good, then the toe angle is probably off. A twist of the adjusters near the ball joints to bring the toe angle in a bit should help. Check the spacing using a tape measure and mark a spot on both front tires. Measure the distance between the marks with the marks facing the front of the vehicle, and then facing the rear. This should help you adjust the toe so that the front of the tires are just about 1/4 of an inch closer together than the rear. If they were much farther apart in front to begin with, that was the problem.
