3.15 has it's own lsd, and 3.31 to 4.56 share the same carrier and can be interchanged.
The strength of aluminum ears is only in question because of the design of the factory mustang mounts, my setup doesnt use bushings on the 4 corners but ties everything together with a solid cradle. But for maximum strength, the iron case is definitely the way to go.
The auto and manual input yoke are different, but swapping to the f250 slip yoke makes this a non issue.
There are several different axles from the factory, ALL of them use 34 spline inner stubs, and 32 spline outer, but have different cv size and intermediate shafts... I provided the part numbers for the v8 shafts, which work work with the racing shafts from summers brothers racing.
Those shafts, like in David's car, are designed around the bigger v8 cv and won't work with the smaller v6 cv... something to keep in mind when hunting for cores to build.
Noah has an aluminum 3.15 diff off a v6 rental car and is using the same 34 spline v8 shafts as david and me.