I may also need a LH rear upright so if some one has a pair we may be able to buy both. As my upright was cracked accidentally while attempting to press out the taper driver-shaft.
I have had a sample of the upright material examined optically in the materials lab at work (Ford Motor Co) this very morning in fact! It does not have graphite but a high content of ferrite and perlite, this is important as it indicates the upright is cast steel not cast iron. Perhaps some one could corroborate?
My research indicates that cast steel can be welded like a mild steel, i.e. it doesn't need a pre or post-heat process. I will be talking to a welder friend as soon as he picks the phone up and I can report back.