dynatrac or currie are good aftermarket but they are pricey.
I also hear you can purchase the JK rubicon axels from mopar performance that are truly bolt-in and they are alot beefer that the TJ rubicon dana 44's. they also come with lockers. I would think a mild small block and JK diffs would hold up and would be the simplest
bone yard 9" you can look at ford trucks from mid 70's to 86 you want to look for one that has 31 spline axels there is a tag on the drop out third member you can decode.
issue with junk yard 9' or dana 60's is the bolt pattern will change so you will need new rims, axel width.
other issues with build your own from boneyard is ..brakes, drive shaft, spring pockets, shock mounts, axel width, off set of diff..ect