I have the Nitro 4.88 gears in my 8.25.
My installer had to grind one of the teeth on the ring gear down, as well as a small portion off of the cross shaft to get the cross shaft in. While this is normal with thick gears and the 8.25, he had to actually cut just a little into the pattern of the ring gear. Before we went through with this, I called Nitro directly and asked if they had experience with this. Apparently, they know about it and said it was the same procedure they follow when installing this particular gear set.
You can see in this image, right above the cross shaft, the tooth that has been modified.
So far, I have not had any issues. I've only put about 1000-2000 miles on them, if that. The gears are a bit noisy on the road. However, after talking to various people, this is to be expected with deep 8.25 gears. Also, the tooth that has been grinded down will also cause a rhythmic noise while driving at certain speeds.
When I ordered mine, I only ordered the one set, along with an install kit and my ARB. The best deal I was able to find, was from east coast gear supply.
http://eastcoastgearsupply.com/i-160580-chrysler-8-25-4-88.html
If you have any other questions, please do ask.
Scott