Here's my opinion for what its worth...
It seems that a lot of people on here say get rid of your 10 bolts for a 12 or 14 without knowing anyhting about you or how you use your 4x4. If your 4x4 is a daily driver and occasional offroader, I would stick with your 10 bolts. And I would find a reputable shop to get in there and fix it for you. If you are a hard offroader or a serious rock crawler, then you may want to go with a bigger axle. Getting one from a junkyard may not always be more cost effective. You don't know what kind of shape it is in or what damage has been done to it. So you may have to get a new axle AND still pay for a diff rebuild. In addition, you may end up having to go to 8 lugs which would mean new wheels. And don't forget that a 14-bolt is bigger with less ground clearance on your same wheels than your current 10-bolt.
I think too many people get caught up in having all the biggest and most powerful parts, and they don't pay any attention to how the 4x4 is used and whether or not its needed. I mean, while you're at it, go get a 500 HP engine, too. I mean everyone must need more HP, right? Who cares if HP breaks more parts than anythng else. Who cares if it is a daily driver or not. Who cares about fuel economy.
Look at how you use your 4x4 before you decide if you need a different axle. But, if all you want is a rear-end rebuild, find a reputable shop and pay the money for them to do it. You don't wnat to be stuck somewhere, whether it is at work, on the highway, or 20 miles offroad, with a busted diff. No matter what size axle.
Just my .02
Brian
85 GMC Jimmy <a target="_blank" href=http://tx85gmcguy.alloffroad.com>tx85gmcguy.alloffroad.com</a>