So In the category of doing stuff that I have the parts for, I decided that this week was a good one to get the differential done. It has been complaining a lot, especially as I take my foot off the gas and coast. About a year ago I got the rebuild kit from I.E and shortly after that I got a phantom clutch.
Now for those not familiar with phantom clutches, I want to tell you everything I know about them... which is absolutely nothing. They are supposed to be a "LSD like" device that you put in the differential to help you with the one tire fire. Pictures are attached. I purchased it for about $300. At the time a true LSD that needed rebuilding (now or in a year or two) was going for about $1500. Including the inevitable rebuild you are looking at 2000-2500 all in. So I will let you know how it goes. One noteworthy item is that it places a good deal of force on the side bearings, so it may eat itself, time will tell.
Also a little surprise... I don't have the factory standard 391, I have a replacement 363 as noted below, which is better for the highway anyway. From yellow markings on the case, it looks like someone was in there before.