I bought my Rk kit used (gen II) and the guy used a plasma to cut them off of his xj. He did his best to make a clean cut but he did still burn into his frame a bit, I think he finished it up with an angle grinder/sawzall.
I still had to clean up the brackets of old weld and pieces of his frame stiffys. Check with prices on RK old brackets, when I called to ask I only got the price of the conversion kit they sell to use their new style brackets which are all bolt on, it comes w/the brackets and the new style heim they use I belive.