it's not the housing, it's the carrier ... I'm not exactly sure where the cutoff is for each model, but it's not unusual.
One thing about doing gears, is that if you're not skilled/daring enough to do them yourself, the install labor is rather expensive, and it becomes a slippery slope. Once you are going to pay somebody the expensive labor to setup gears, you might as well install a locker at the same time, and if you're going to spend that much money, spending it on a Dana 35 is like throwing it in the garbage, so you might as well upgrade your whole rear axle while you're at it. It gets real expensive, real fast.