[mosesburb]

As you found out, those bolts typically break because of insufficient u-bolt torque. Now that you have them torqued, re-torque them after the next five (or so) drives you take in it and notice how "loose" they are going to be. Seriously. Any time I do work that requires u-bolt removal, I will re-torque them for the next week until the nuts don't turn anymore at the specified torque. If they are loose, it doesn't mean they stretched, just that things have moved around slightly and by default "self-adjusted" their torque values. Re-torque them until nothing moves around anymore. It usually takes me about five times to get them all good. Also, oftentimes one out of the four nuts will require re-torque, not necessarily all of them.