I ran into the sane issues when going from 17" to 18" tires this year. I was looking at 18" rims at Discount tire and the guy doing the research actually called the manufacturer of the rims I was interested in. Ironically one set that was rated high enough was not recommended according to that manufacture since I was towng a 5th wheel. It took awhile to find the set I needed that had the right weight ratings. I too found lots of cool looking rims with 2200-2500lb ratings even though they had 8 lugs which according to Les Schwab was all you needed to worry about. Pays to shop around.