8 3/4 to Dana 60

Only if I'm using existing dana 60 parts, correct? If I am having a new S60 made, is there any reason I can't have it set up to use my existing brakes?
Talk to the person/company building your rear. If they can do it, go for it.
With the A body brakes, you're stuck with 10x 1.75 shoes.
With B body you get 10x 2.5 or better. Your call.