It's been a while but I believe it is the inner race that is longer. I have had trusted reports that they do make a difference. I did the front axle trick on my LS and I am sure it made a difference. All the little stuff adds up. (You machine the big part of the axle back so that both sides of the other slider pinch on the axle versus just one side of it.)
Personally, I wouldn't worry about that drive shaft spring. Sure they rarely fail but so does everything. Of course, the solid ones are lighter! I have seen the spring in the transmission fail at least five to one more times. I think that's what the spring on the drive shaft is suppose to be saving. They beefed the trannies up a lot there around '86? Good luck!
supershaft screwed with this post 10-24-2012 at 12:00 PM