A u bolt is a bolt bent to a U shape. The lock washers should be replaced if they are not still "spread". Other than that, you can reuse any bolt in it's former place if still in good condition. Those quotes are BS+. Rolled threads are not prone to any more "distortion" than cut. The washer keeps the nuts tight. You don't get accurate torque with an impact, that we all know. You use a torque wrench. The part about salt, road and rust is the "good condition" part. It never "hurts" to use new bolts if you have the money and if you believe they are better. IMO: replace, in a manual, means put the stuff back on, unless they use other modifying words like "new".
Thank you, I agree completely.
As a materials engineer I can tell you that bartamos is right in calling those quotes BS, and he's correct that the statement about rolled threads is false. If the bolts are in good condition, you can re-use them. If they're not, replace them.
If there is that much distortion on the threads, then they likely will get heavily damaged when you take the nut off, or attempt to.
