I faced this issue recently, albeit for my 9" Ford rear end, and I went with a PowerTrax No-Slip. For those not in the know, the No-Slip is a civilized form of locker you can install without having to have your ring & pinion set up.
From the Powertrax Web site (
http://www.powertrax.com/index.php/p...trax-no-slip):
"
It combines the smooth operation of a limited-slip differential, with the traction performance of a locking differential.
A precise synchronization mechanism eliminates the ratcheting sounds typical of other locking differentials. Special gear and spring design reduce the backlash and therefore driveline windup. Only ultra strength material is used which is 67% stronger than titanium.
Installation is simple because no ring and pinion set-up is required."