Some ideas and questions about the FORD 8.8 axle:

Yes on the ratios 3.23, 3.55, 3.73, 3.91, 4.10. The L is for limited slip, or a Locker as Ford calls it.

Doing what your suggesting would be adding length to a short side tube. Easier to cut and shorten, than to lengthen one.

Yes you use 2 short side axles to shorten the axle to A body width. Cheapest way is hit the pick n pull. Remove the long side axle on the prized rear your intending on buying, load in a short side axle from another xploder 8.8, reattach the brakes, or better yet, temp install reconditioned brakes with new or turned rotors from yet another exploder in the wrecking yard to maximize what your buying. Pick n pulls dont care. Is it an axle complete flange to flange? Sure nuff.