Well I am certainly no expert on this but,since no one else has answered I will put my two cents worth in. First I would check the loader mounts to make sure that nothing there is out of place. If you stressed something so hard that it bent the loader then you have to make sure that the rest of the tractor is good. Check the whole tractor closely for anything, cracks, even cracked paint, broken or loose bolts, cracked welds. Check the uprights for the loader to make sure they aren't bent forward or backwards or to one side. If every thing so far is plum level and square to the tractor, then it is just the loader arms that are bent. I would probably try to straighten them on the tractor, but a smart guy would strip the cylinders off the loader then disconnect it from the top pins and lay it on a flat surface to see how out of wack it is. If it is twisted sideways then all you have to do is twist it back. Simple? Not likely. You tie three corners down and jack the fourth up to bring it back into line.Now if you have pushed one side back or bent one of the arms it makes it more complicated. Even if you get it back to its original shape it will never be as strong as before unless you weld some bracing in. Good luck, Let us know what you find. Maybe some one else will jump in with some better advice.
Dusty
