Gotta take some weight off of the headstock (yeah, another neck dive post). Only requirement is the new heads have to be black chrome or in that vein to match the guitar. Grover never got back to me about the weight of the rotomatics, but I understand they're pretty heavy. First choice would be something that I don't have to drill new holes for. Second choice would be something like stamped vintage tuners like Kluson has, but I don't know if you can just grab any 3+3 machine head and throw it onto there.