I've heard other competitive users say that sheer force is the better choice on Gurdurr and Conkeldurr, and I agree. Especially since you'll be using an eviolite, I would use sheer force instead of guts because you'd have to have your opponent use status moves on your gurdurr for it to activate, which, if a status move fails to land, your opponent will know what you're trying to do and prevent it.
You should also be aware that sheer force will only boost poison jab and thunder punch. Priority and moves that lower your own stats are not changed by sheer force. I'd recommend changing hammer arm to something stronger such as superpower, since your stats are lowered anyway. Superpower is unaffected by sheer force though as well, so it all comes down to individual choice.