the u-bolts on my 88-440 truck came from my 68Dart,went on my 85 truck,then moved to my 88 truck.

I have always reused the u-bolts if they are long enuff to fit the bill. and when too long I have cut them down.

only time I use new ones are when i need longer ones for a lift or something. then just have the spring shop make up new ones.

I have had them rust up and the nut seize up and twist till they broke..I did/would not use those again.

Guys over on RCC say Don't reuse do to the fatigue of being tightened and "stretched" so to speak. I plan to use new as its a cheap insurance to not looking my axles

The factory u-bolts had interference threads on the nuts (the nuts have a small hole stamped in them). You put them on and you were not suppose to use them again, they were made to stretch the threads. This was done so they would never back off.

When you get new ones at a spring shop they just give you lock washers and regular deep nuts. I would and have used them again.

Before spending any money, I thought I'd try a few different zero dollar tweaks.
The first idea was to swap the spring packs from side to side. I figured that the job should take a few hours total. The previous owner had installed longer shackles at the rear eye many years ago and mounted the springs in the center bolt hole. On a whim, I decided to move the LH (Low side) leaf to the lowest hole. The holes are spaced 1 1/2" apart. I figured if it made no difference, I'd go ahead with the side to side swap. The truck now sits only 1/4" lower on the left. The fix lifted the left corner almost an inch. Thats close enough for me and it didn't cost anything.

Fix my '84 W100 by replacing left front spring and putting a single air shock on left rear.