Duster rear suspension issue

74 Duster with new shocks all around... nothing fancy just OEM replacement.

While driving the new shocks have made a huge dfference in handling and noise. However, when I hit a larger pot hole it sounds like something is coming through the passenger side rear seat area. sounds horrible. Small-medium bumps and RR crossings don't seem to make it happen.

Any idea what to look for? The springs all look ok with the clips, etc. The rear mounting of the springs has what looks to be 3 positions and they are connected in the lower of the three locations.