I've re-arced my own leafs to correct some sag in the original leaf pack.
I had a single leaf break on a Tundra, and picked up a used leaf and arced it to match the other side.
I've de-arced leafs to sit lower in the past.
I have no problems with a used leaf pack, and it the pack is the SAME as what you are replacing, I see no problem. Make sure the used pack looks good, eh? Like: minimum corrosion or pitting.