Anybody use a locker?

[71chevylowrider]

I'm trying to decide the best way to put posi in my truck, according to richmand gear the Power Trax Locker is easy to install & makes my current 12 bolt 3.73 non-posi rearend, POSI! It sounds good to me, I've been looking for a used 12 bolt 3.73 posi rearend for a coil spring truck (mine) but for the money I could buy a brand new locker unit & install it myself, & if I bought a used one, I wouldn't know how long it might last before it had problems, anbody have experience/opinions/advice on this? I'm kinda embarrased that my beautiful, fast truck can only leave one black stripe when I get on it. Or I can't get enough traction with one tire to really appreciate getting on it. Any help/advice would be greatly appreciated.