The Detroit Locker unit (sold by GM as an option, I think they called it NoSpin) was available as an aftermarket part, too. I have one in a 4.57 differential, it's going to be installed in my 4.10 open pumpkin. It's the only one I've ever seen on eBay in four years of looking - but I got it for the opening bid. From what I understand, the DLs will work in any of the 47-72 Eaton H0xx differentials.
