Sorry to hear about your problems; unfortunately this is quite a weak link for an for what I hear is a otherwise good tractor. I am in no way an expert in Masseys but I have heard a number of options that have been explored for this problem. I know one person that sold one out of sheer frustration!
1. Have the unit rebuilt if you can, this will be expensive and make sure that the rebuilder has access to the many service bullitens that came out on the unit ( good idea for anything mechanical!), they tried quite often to ring out the problems with the unit and at least rebuilding it with the updates gives it a better chance of working longer.
2. People have gone with "converting" the tractor to manual steering, not the greatest option unless you need to build up arm strength real fast!
3. Converting to another manufatuers (eg. Ford) steering system, this is not guarenteed to work or look good and probably would take quite a bit of modification, but desperate people will try anything!
4. Some people have tried later model front ends (I belive a 245 will fit but do not quote me on that ask an expert!) that is of better reliability and of which you can more easily obtain parts.
Hope this helps!