[fordteacherguy]

I run a Broader 2.92 set and also have a ATI 2.92 set C-4. The Broader set looks more robust than my ATI set and held up for about 3 years of hard abuse before it looked like it needed rebuilding. The actual planetary is from a 125C GM, so I just rebuilt it using those parts every few years. But last I heard that set may or may not be available, check Broader Performance website. Good guys.
Where the Broader stuff uses Ford hubs and GM gear sets the ATI uses GM hubs with Ford splines pressed and welded in and just gives you GM clutches to make it work in a C-4.
I haven't used my ATI set yet but, it looks like it will hold up ok. Wasn't as impressed with what I got vs the Broader set up. With all of the C-4's the front planetary is the weak point usually with thrust washer wear on the side of the planet pinions. There are limited manufacturers of the 2.92 sets for C-4 and I haven't seen a 6 pinions 2.92 set yet. If you can find ones with Torrington bearings on the planet pinions even better. Maybe some others can chime in.