The two Sure Grip types can be interchanged between the carriers if the matching differential axle bearings are retained. The outside diameter of the cups are the same between the '741'/'742' and the '489'; the inner cone differs.
Hey thanks again for the great information. Sadly though, I think I'm reaching the point where I'm going to put it up for sale. I still have house projects going on and I need to re-restore my '72 Fury III with 48,500 miles on it. It was pretty close to being a show car and surely turned heads whenever I took it out. Now, that has sat too and I need to go back over it. I actually have 2 build sheets, fender tag and a couple of records of its past. That one is stored over my son's house under a carport, where my barracuda was in my dad's garage, but got moved out for me, which I found out when I went to look it over and get pics.
It's a really, really hard choice as the Barracuda was my first car and a 69 340S fastback has been my dream car since I sold the first Barracuda back in high school. However, I learned to drive on early 70's Furys and the one I have is very close to how it left the showroom floor. If I had that kind of documentation for the cuda, and it showed it was an S, then I'd keep it and sell the Fury (at a big loss). Pics of Fury below,
Got some thinking to do, but I feel it going to have to be the Barracuda go. Sucks.