I've used car-part.com to hunt down junkyard 4.10 axles. my go-to for up to 33s is the late model XJ 30 paired with a liberty 8.25. but the liberty 3.73 geared axles are like 95% of them out there, so if you go that way, any yard will have one (so be picky and get a good one). 3.73 is common in ZJs and TJs front axles (though they will be low pinion). ZJs and TJs usually have a 35 rear, which I would skip. or the silly aluminum 44 in the ZJs which is arguably not any better than the 35.