4.0L's did not come with 4.10's. If you get a Ford Ranger XLT you can get 4.56's but with drums (abit larger drums then the D35c.). The Explorers with the 4.10's were the 4.0L. Post 91's will have the 31 spline shafts and discs. Before that they used 28 spline shafts.
Your only limitation right now is the Dana 30 since you have a 9. Either swap out that D30 for a 44 amd go deep or just gear everything to 4.88:1.
I was told that the XJ's with the auto and towing pkg. came with 4:10's though?
As for the 9", I'm sticking with 4:88's. They turn my 35's fine and I'm still a little under 3K at 70 MPH. I can get 4:86's w/ an install kit shipped to my door for right around $200 (A guy on JF I talk back and forth with regularly has had good experiences ordering from the guy).
I actually just went out and tackled those spring perches and shock mounts on it. They came off easier than I expected
I haven't convinced myself I'm doing the swap, but I seem to be working on the axle regardless lol. All I need to do is order an axle swap kit from Ruff Stuff Specialties and I'll be able to dial in my pinion angle while I wait for the gears and what not to come.
Again, for some reason I'm talking about all this work even though I'm not 100% sure I'm doing the swap. I think this is my way of talking myself into it