Never done it myself, but here are some references.
"Well, I need to clarify something concerning cone type SG's and their lack of being able to be rebuilt. They can be and there was an article in High Performance MOPAR Magazine, May 1997, PGS 28-30 where they did it. They removed 0.080" off each cone in a lathe and installed a 727 high clutch piston return spring (one each) into the center of each of the four original springs. The article is fairly easy to follow with good pictures."
http://www.4secondsflat.com/rearendtech2.html
"Cone-style Sure-Grips are worn out when the cone clutches bottom-out inthe case. To inspect this unit, the differential was dismantled and thenreassembled with some clay at the clutch-cone ends to gauge theremaining clearance. We found .060 inch, which indicated plenty ofservice life left. If the clearance is near or at zero, the clutcheswon't grab, and the limited-slip function will not work. Machining thecone ends and adding spacer shims behind the side gears can breathe newlife into a worn cone-clutch Sure-Grip."
http://www.moparmusclemagazine.com/howt ... index.html