On my MH a similar thing happened on the rear air bags. We hit a large pot hole causing the air bag mount to bend up bellowing the air bag. The mount was only mig welded to the frame and the weld didn't hold. Mine was not bolted on just welded. My mechanic removed the duals grinded off the remaining weld and removed the bracket. He then heated it up with a torch and bent it back into shape. He stick welded it back on making sure the metal was properly fused together. He also put two #8 bolts on as well with a rectangular extra size washer/plate on the backside to to spread the force across more metal in the event of another similar incident the frame would not split or tear at the bolt holes. To fix your situation the frame can be fish plated and reinforced at the split. Then again weld and bolt the upper bracket on with a bolt back up with a larger rectanguler piece of metal as a washer to diffuse any further incidents and spread the force along more of the frame rail. Rather that just where the bots are.
In hind site the weaker welding method on my F53 saved any frame damage.?? Or if it was done properly initally there would be no damage.??