I'm using a 3:7 lsd, and I think it's just right (rpm wise). Granted, I have not ran it at a track, but I have done quite a few country road wide open pulls, so I think it will do fine once I finally take it to a track.
I have a 4:11 clsd that I have not tried yet, so if I find it's needed down the road, I already have one....
I think you will benefit from stepping up from your 3:3 diff though...