A 9" housing must be back-braced for strength, as the tubes are welded to a sheet-metal housing. I bend/straighten NON back braced (circle track) fab 9" housings in my hydraulic fixture very easily.

Because the tubes are press fit several inches deep, then welded around the circumference to a rigid center casting, a Dana 60 housing takes much more pressure to bend/straighten.

The Dana 60 pictured in this thread with Cal-Tracs and blue shocks is a perfect example of an application where a back-braced 9" will not fit and a Dana 60 is probably the best choice.