For the 4R100, you'd get the E4OD case from a big block truck or van and have the internals upgraded. Much the of the same stuff (actually, both are pretty much a C6 with overdrive). One warning, either of these OD's are massive in size and weight..
The aod has been proven by several people on here to live behind a decent big block with the right mods, and it is living behind 600+ hp turbo small blocks fairly regularly..
Jim