Whenever rebuilding an axle, ALWAYS replace the U bolts.
While they may sometimes look okay, it just isn't worth the chance to re-use them.
Any good automotive store can get you new U bolts.
They may not have your size in stock, but since they are custom made anyway, it is no problem fitting the correct bolts to your axle.
On mine the factory must have gotten a deal on some extra long U bolts...Or someone just couldn't measure very well?
The bolts were so long, that extra washers had to be used on all, and a steel shim had to be inserted on one side to prevent bottoming the nut at the end of the threads before it was tight.
No big deal I suppose, but they forgot to cut off the excess threads, which over time, damaged the trailer frame.
On underslung axles, the U bolt heads point up toward the trailer, on overslung axles, the heads point down.
Rubbing the pavement isn't such a good thing either...Cutting off the excess is the best option.