Found! Bought new from RockAuto - Needing a left (driver's) side axle for an 8.8" 31 spline Torsen differential.

[Rimjam]

Bought a Torsen rear diff from an '04 FX-4 Level II but missing the left axle. Anyone have one they're willing to part with?

 

[Rimjam]

Decided to not risk modifying an Explorer shaft & bought a new axle from RockAuto. Arrived two days early. Cost a little over $200.
Thanks for the heads up pjtoledo.
FYI: Overall length is 30 1/8 " from 'button' on carrier end to outside edge of flange where inside of brake drum sits.