[buffydores]

A good 6-lug upgrade is a 14 bolt SF (9.5"). It's just beefier. We're just setting one up for a buddy that's working on his '90 Burb. You can find them in OBS 1500s with a GVWR of 9,500. Hunt them down on Car-parts.com. All of them have tons of miles on them, so you'll spend some coin to rebuild. Instant brake upgrade out back. Run a Truetrac and alloy shafts and you're good to go out back. B&M has a nice cover that helps reduce flex inside. Upfront, I wouldn't stress too much unless rocks are your deal. I like the alloy shafts because breaking shafts and seeing your wheels come off is unnerving on these c-clip axles. The 14bsf is just a more rigid box. Less likely to go boom.

Personally, my 12 bolt in the K5 runs a Truetrac and alloy shafts. I have the fancy cover also. I have the NP203, so my power is split front and rear always.

EDIT: I just re-read your post. I don't think you need anything. But if you must, just rebuild a 6-lug 14 bolt SF and add a Truetrac out back. Nothing else. I don't know why in the world you'd want to mess with the front diff if you're not doing much off-roading. There's no point.