I think with a light sled, you could pull off a 3rd gear launch in 4 low. The key with the stock clutch is to launch low in the rpm. Bring it up to around 1600rpm, come out on the clutch some and get moving just a little, and then mash the throttle and come off the clutch all the way at the same time. It may take it a second to get back up on the turbo, but it should do it unless the sled is real heavy. 2nd gear would be easy to do, but you wont have hardly any speed at all.
Eric