MJ shackle Mopar part number 52001828.
That's a real stock MJ shacke.
It's available from one online parts place I found for around $52 each (plus $8 shipping) and from Jeep dealerships for $82 each (free shipping). http://www.partswebsite.com/moparonl.../52001828.html
Comes with new bushing installed.
Provides 3/4" lift. Is great for low lifts that use new rear springs (like OME) because it allow spring to stretch out a bit more during compression.
Unlike most aftermarket shackles, it's only 3/4" lift, which is about perfect to match a low lift spring of 1.5" to 3".
For a taller lift spring than that, you'd probably want a longer shackle. For a lesser height lift spring, use stock XJ shackle. IMO.