For 3"? Probably won't need a new Pitman (I had a 1987XJ with 3", 31s and stock steering - no trouble. You can install a drop Pitman if you like, but I doubt you'll need to.
You're borderline for needing to go to a Tcase drop or a SYE to improve driveline articulation, but you have a bit longer rear shaft (therefore shallower angles) in the MJ than you do in the XJ, as I recall. So, less of a problem there. A tcase drop is easy anyhow.
I'd avoid AALs for the rear - they make a rough ride (especially unloaded.) Blocks merely accelerate spring wear, in most cases. If you're going to do coils up front, why not get properly arched leaves in the rear? And, if it were my truck, I'd put airbags in the rear, since I invariably use trucks for hauling (and airbags can help 'share the load' with springs, and give you more time before they sag.)
Brake line extenders? Get them anywhere you like. I suggest a vacuum bleed when you're done, instead of a gravity bleed (a pressure bleed is best, but the gear costs more.)
Those are my scratch thoughts, anyhow.
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