I could swear I saw them in the Man-itAint-Free catalog. Or was it SOR. I've heard both good and bad but the only one I saw was on a 40 in Moab and the guy showed it off by skidding the rears. I was surprised after hearing people complain about them. He said he had two output seals in there now. I like the sound of that.
I've heard the same things. Sounds like a good idea, but apparently it has problems. There is a company that makes a speedometer housing that will hold 2 output oils seals. Can't remember who makes it, but iirc, it costs around $65. Maybe someone else remembers who makes it.
I too have heard the bad -- the parking brake on the rear drive shaft sounds like a good idea but as an old cruiserhead told me - if you hang up on a rock and bend the disc you are stuck - the drive shaft won't turn any longer. Plus, the calipers for the drive shaft application is reportely a "go-cart type" unit - can't be too strong. If you don't want to stay stock - suggest converting the rear drum brakes to disc and use Cadillac Eldorado calipers - they have emergency brake capability built into them. TC