Steelix max speed at Level 100 with 252 Speed EVs and Jolly Nature is 174. Though that seems high, it is not in the grand scale of things. Speedy Steelix is not a very good idea.
Even with Choice Scarf, it only has a speed of 261. Being locked into one move is not good for Steelix. If you do not give hime a + nature, it is 156.
Last point: It is not a good idea, but it is your choice in the end.