65 lower control arm u bolt BROKE!!!

[65shortbox]

Here it is in the parking lot waiting for the tow...



I was exiting a parking lot to a busy street where I could not see oncoming traffic so I decided to back up and exit from another driveway. I turned my wheel all the way to the right and backed up when I heard a BANG and the wheel cut hard right. I was able to back the truck up out of the exit, got out to inspect, and I saw that my lower control arm U-Bolt had snapped! This would have been bad at highway speeds! Do you all have any explanation as to why/how this might happen? Just old parts? Maybe upgrade to the larger '73+ style LCA u-bolts? I drive this truck with my kids often and I don't want this to happen while driving. I just had the alignment done and this was my 3-4th time driving it since. Also, after I converted to disk breaks up front, I started to notice a clunk sound on occasion when I would cut the wheel hard right, left, or stop in a parking space (only occasionally). Any ideas how to make this stronger for safety sake? Thanks in advance

Here is a shot of the tire...


Control arm dangling to the floor...