I had the same problem with my 18x9's in the front. They hit the stock A-arms at full droop and full lock in either direction. I installed a set of Magnumforce non-adjustable bushed UCA's, problem solved.
Any of the "V" shaped tubular UCA's should be fine, and should take care of your problem. The only one's I would avoid are ones shaped like a "U", because they may not give you enough clearance. I know the Firm Feel UCA's are "V" shaped and should work fine. The earlier RMS UCA's were "U" shaped, but I think they've updated their design since then to increase clearance.