Mine has a custom 8.8 fab for my 98 that I build. I have Yukon 4.10 gears, Moser 31 spline axles, 9" housing ends so I could eliminate the c clips (<<a major weak point) and a Moser rear cover. Making it was not an easy job, I had to get a welder that could tig weld and know how to properly control heat when welding nodular iron. If not controlled correctly it will crack the welds.
Once it get's everything broke in and running right I'll be looking into a wave track differential for it now that they make one for 31 spine 8.8's.
Too answer your question on difference between 9" vs 8.8's. 9" are incredibly strong and their design enables for quick gear changes/repairs (if you have a spare) at the track. 8.8's can be close in strength but have less parasitic drag and weight penalty over the 9". Before 9" became popular, it was the 8.8 that was sought after.