I would replace the G80 since so many have failed. Go on Ebay and you'll find used limited slip differentials available there for around $100. Nobody seems to make gears better than those that GM installs. A factory set of take-out gears should work fine for you if you can find a set in the range you desire. Richmond gears are nice and quiet, also. 4wheelparts.com sells the Genuine Gear line and the prices are around $150 a set last time I checked. If you swap them yourself, start out with the exact same setting that the factory had on your old gear set. The factory parts maintain very tight tolerances on the rear ends and a lot of times you can swap gears and diffs with all the same shim packs from the original setup to the new one and you don't have to make any adjustment. The 14 bolt rear should be fully adjustable without buying any shims.