Ice Punch covers grass as well? It also gives Dragon/ Flying/ Ground coverage. Fire only gives Ice/ Bug/ Steel which isn't relevant when Golurk is resistant to Bug and has Drain Punch.
Realistically Thunder Punch should be swapped out for Earthquake, unless Gyarados is a massive threat to your team (then again I can't see Golurk being a viable solution to Gyarados). Only covers Water, and you don't want Golurk to stay in on a Water Pokemon anyway.