You can swap the traction loc differential from a Mustang GT into your 8.8 rear, no need to swap the whole rearend. This can be done in a half a day on your own, with no special tools. You will need instuctions on checking the ring gear pattern after you put it back together, I don't think you'll need to change the pinion depth afterwards. Basically what you'll be doing is removing the rear cover, pull the C-clip off the axles, pull the axles. Unbolt the four bolts holding the differential in the housing, then swap your ring gear between the open diff to the trac loc diff, then put it back together. Then check the wear pattern on the ring gear teeth and make adjustments as necessary.