Best IVs for Conkeldurr would be high ones in HP, Attack and Def/ Sp. Defence. It's Sp. Def is already low (at base 65), so yea, 31 IVs is brilliant for it.
Speed and Sp. Atk don't matter at all, so you can pretty much ignore those stats, but I would try to get one that has higher HP/ Atk. Afterall, Conkeldurr would be a physical sweeper, but its appalling speed means that it needs HP investment in order to say alive.
Also, try to get one with Guts instead of Sheer Force.