I was fortunate since I know the owner of Outlaw. He happened to have a set of spindles laying around from an F150 that had installed a 6" lift. He had them welded up and shipped to me and I just swapped them out. It kind of sucks as you have to pull the spindles to have the gussets welded. Might be worth checking with a local 4x4 shop like 4wheelparts and ask them if they have any take of spindles or check if outlaw has a set. The gussets themselves are only about $100.
Are they worth it? Hard to say, I wanted the extra protection/piece of mind since I do a lot of offroading in the middle of nowhere at speed. I can say that over the past couple years of Desert runs we've only seen 2 failures. First, guy hit a nasty washout at 30mph (was going much faster but around that speed by the time he hit it) and it snapped the spindle. Gussets probably would have helped and may have saved the spindles
2nd, same guy was power sliding around a turn and the rear hit some soft silt and kicked out. Flew of the trail and on to a boulder field. Nothing would have made a difference on that lol. In both cases, the driver was pretty much over driving his truck for the conditions. But, that's often when most people get into trouble. Everyone likes to push the boundaries.
All that said, you're probably ok without them but if you want the extra piece of mind they are worth it IMO.
Hope that makes sense and helps.