This is a very common problem w/ the SS. Once you get some DR's on w/ traction or higher HP you'll start to overpower the clutches in the rear end and get the one wheel spin. Ted Jannetty sells a posi mod that corrects this problem.
http://www.camaro5.com/forums/showthread.php?t=126085
http://jreperformanceparts.com/techn..._store=default