Well, after reading a lot of threads about different lockers I decided to go with a US Standard Gear Spartan Locker. Like any lunchbox style locker, it goes in the place of the spider gears. The install of the locker was very easy. I used the thread http://www.explorerforum.com/forums/showthread.php?t=318076 to help during install. The locker came in a nice box. It came with a set of instructions on how to install the locker inside the open carrier. The Spartan Locker DID NOT have to be modified in any way to fit the ford 8.8 IRS. The axle spacers had the correct inside diameter. Not the best way to measure the inside diameter but hey, it worked. Getting the diff out wasn't all that hard. I had a buddy with me helping getting it out. I cleaned the inside of the diff with break cleaner (not perfect) but I got the major stuff off. Btw, the tolerance for the Spartan Locker is between .145-.170 inches. That was measured with feeler gauges. Do not use thrust washers for this locker. It specifically states not to use them. So make sure you get them out when you remove the spider gears. After install: After you get everything back together, go have some fun!!! It works excellent. NO problems. I don't hardly hear it on the road. You can hear it when making sharp turns in a parking lot. I used Lucas 85w-140 gear oil. And if you have a noisy rear end, this gear oil will help lessen that noise. It is about 10$ a bottle and you need to get two. (Ford manual says to put 1.7 quarts in rear axle) Any questions, feel free to ask.