Eaton Gov Lock or posi unit? If its anything like all the other GM diffs, you must remove the pinion shaft retaining bolt. to get to it, use a box end wrench. (5/16"?) If you spin the carrier, you will see the head of it, facing the passenger side of the truck. Once thats out, push the pinion shaft through the diff, until the axles are able to be pushed into the space once blocked by the pinion shaft. Then the C-clips will drop off. Due caution with the pinion shaft..if its in tight, and you push it through so it wedges on the pinion gear, you are going to have a hard time getting it out without pulling the whole carrier out.
Dorian
My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://yeagerd.home.mindspring.com/index2.html>http://yeagerd.home.mindspring.com/index2.html</A>