Went back and looked at some frame rail and UCA mount pictures. So on your car the rear leg of the UCA on the bottom was contacting part of the frame rail? Just where the sections of frame rail are folded up? As long as you're not removing any spot welds there's no reason why you can't trim that area. Most of that lip isn't structural, it's just left over metal. Even if you found there was a couple spot welds in the area of lip you wanted to remove you could just weld the halves back together after you did the clearancing. That would be a car to car issue and whether the UCA was "U" or "V" shaped there wouldn't make much difference. Neither would the bushing vs hiem, unless there was a long section of heim threads exposed to move the thicker part of the UCA further away from the frame. But that probably wouldn't work entirely either, since if the rear leg is adjusted all the way "in" for caster even the heim set up wouldn't be long enough to clear that lip.