Got to ask, why is the seller selling?
If seller is not a wheeler upgrading the axle, thus assume he's just replacing the axle do to the fact its bent.
For the price, I wouldn't look at it. There are too many hidden 'faults' that could make it not worth it. Same for your offer price. Even for the disc brake setup.
Better off with 8.8, a TJ D44, or even a D44 from a Scout or Wagoneer. Yah, to get to the non-stock axles under the TJ, you will require welding on brackets, regear, locker choice (automatic (case/lunchbox), manual (air-ARB/cable-Ox), limited slip), wheel spacer, yoke-joint match to rear ds, electrical switch/air compressor setup (if going with ARB locker, cable/shifter is included w/ Ox locker).
All these options for what kind of wheeling do you do?