Just went thru one version of this - 3905 diffs - ebay, one was $19 other $21 shipped, so the pr was $40. I'm going to run them without taking them apart, but prob a mistake - they feel like they need shimming. Haven't installed front yet, may break down and look inside and check it out.

I have done the other route using flm diff cups with their modded ring gear and new pinion - those are $30 each. Strong enough for a 28 nitro, but how well stand BL power, don't know.

Muggy diffs - no idea.

UE - 6 sypder diffs used runs $150 and up, may find cheaper, ebay or UE BST easiest places to locate. They are in stock at UE, new at $260. The 8 sypders start used around $175 and new they are $299 (new, in stock).

The flm hybrids - cases are $140 and you'll need a pr of diffs and pinions at $60 - 65 each so parts will total $260 or so.

Which is best, thunk the UE 8 spyders is the absolute best/strongest, they still need bulks however which the hybrids don't You could buy the ofna 8 spyder diff and pinions and put them in the hybrids. The cups hold up better than stock, not much else can say about them.