I suggest going with Trick Room Steelix. As you said, its Maximum Speed total is 174, which isn't even close to outspeed a bunch of Pokemon. That is why you should use Trick Room, because it's Speed is so low(measly 86 as lowest), that it can outspeed anything when under Trick Room. Also, if you use Rock Polish, you still won't be able to outspeed much considering Pokemon run Choice Scarf and have high Speed Base total.
So for this guy, I suggest rolling with Trick Room.