I believe you want Lock RIght #1830. I saw
one at $360--I guess low demand makes that one a little more than other axles. It's a couple hours to install, maybe an afternoon if you haven't done anything similar before. No special tools or knowledge required. Actually, come to think of it, with that little ring gear you may have to grind a tooth or two a little to get the pin out. I've not done it, but I almost did and the owner balked.
A quick way to tell if you have a 7.5 or an 8.8 is to slide under the rear bumper and feel the bottom of the pumpkin right under the cover. The 7.5 has a narrow 3/4" wide lip cast into the housing along the bottom of the cover--like a handle you could use to pull the truck backwards. The 8.8 has a thick lip under there--maybe 2-3" wide. A picture posted here would quickly clear it up if you aren't sure.
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