If you're doing this, I would have to go with a Choice Scarf and enough speed EV's to outspeed what you want.
I did a set to outspeed a Weavile with Max speed on both:
@ Choice Scarf
Mild/Rash | 120 Spd, 252 Sp Atk, 136 Atk
-Waterfall
-Dark Pulse
-Ice Beam
-EQ
With this set, you can outspeed Weavile with 384 speed. With Max IV's for both attacks, you're running 317 Special Attack and 310 Attack. As any wall that might switch in would be Physical, max special attack would be best. If you must, run Surf on the first slot, due to the 7 points higher in Special attack. I like Watefall due to flinch, but whichever.
If you don't run Choice Scarf, max Speed and Life Orb for a mixed or Choice Band for an all physical set is a must.