Well I really the only ones that are worth getting with that nature are bronzor, and munchlax which have 2 abilities, a ability 0 means thick fat SD munchlax, but heatproof bronzor, and ability 1 would be the opposite. Then for duskull and beldum it won't matter. Although if I get a onix as well, I would hopefully get ability 0, since that would be rock head