Using 8 3/4 with /6

I looked on summit and ebay; Motive and a couple other mfrs still sell ring and pinion sets for them (3.55, 3.90, 4.10)...kinda surprised actually. They are a little pricey though--about $250-$300. Also saw a set of NOS 3.91 gears on eBay for $175. And I have seen SG units in the classifieds, but they come and go quickly.