So that's what you've been up to all this time? Causing headaches for yourself?
Obviously you can tear it out and put in a chromolly torsion housing. You also could probably plasma out the nut (or threaded deal) in there right now and weld in a new one. Or you could cut out just the inner pivot housing and weld in a new one (ie IRS conversion kit). Maybe retap to a larger thread and have some new bolts machined (assuming you can't find the ones you would need anywhere off the shelf).
Maybe someone else will post up a solution that offers a simpler, more intelligent approach but these are all the most viable ones I can think of. I wouldn't think it'd be very plausible getting a nut on the end of the bolt somehow...?
What if you fabricated something that would just hold the bolt on by pushing on it from the outside? Know what I mean? Not really the "right way" but no reason it couldn't work.