'66 Barraduda front suspension won't adjust down one on side

yes, that is correct. the adjuster moves the anchor of the bar-- which the bushing is pressed into. this is why it's critical that the LCA pin nut be loose when adjusting ride height, otherwise the bushing tears and fails quickly.
In my case, the arm and the adjuster bar/anchor are rusted together, thereby not allowing any ride height adjustment. I hope to have it freed up in the coming days.