A B C E Which housing?

Really depends on what you're looking at for rear rims. Barracuda's have more room than Dart's in the rear wheelhouses, but less than Dusters/Demons. The 65-67 B body rear is an easy fit, and the 68-70 B rear won't be a big issue. But as already pointed out, you need more backspace than stock. If you want to run 17 or 18" rims, that's a good thing, as you'll have a lot more "off the shelf" options. But, if you're looking at running 14 or 15" rims, you won't have many options without going to a custom offset because the smaller diameter wheels just aren't all that available in large offsets.

So, if you're trying to get a set of 15x10's back there, you're better off buying the rims you want and having the housing shortened. If you're going to run 17 or 18" rims, you can use an uncut B body housing and you shouldn't have any problems finding an off the shelf rim.