A limited slip is better than an open diff in most all situations, it will increase your chances of having both rear tires helping you move forward. It's not 100% lockup like the lockers you mentioned but it does send power to the tire with less traction, more so than an open diff. A limited slip works pretty well with up to 33" tires, anything larger and the increased leverage of the tire generally overcomes the benefits of the clutch pack inside the differential.
Yes, you will eventually be replacing the entire LS carrier with the lockers you mentioned, so it may not matter what carrier type your new axle has inside.
Be sure to have somebody weld the axletubes to the diff when you get the 8.8, I did my own with 55% nickel rods in my Arc welder, worked great.