Leftovers is a good option, since it gives recovery. If you get into a nice sweep, then leftovers can bring up your health nicely. However, if you are able to take hits, I say go with the Life Orb. If it can take hits, and you can get up one or two Dragon Dances, it should be able to outspeed most pokemon besides ones like Speed Deoxys, Jolteon, etc. Sheer Force also takes away the recoil from the Life Orb as well, I believe.