by Warkton Tornado No.1 » Tue Mar 09, 2021 9:48 pm
It is difficult to reshape castings back to the way they should be, especially as distortion may have occurred through the ageing process - a form of stress relieving.
It may be the case that with a well made device, such as a jig of some kind, you could replicate the correct hole centres & induce the headset top to spring back into shape using longer screws not made of monkey metal. Obviously, as soon as any jig was removed, you would be back with the misshaped top!
I believe that the trick is to utilise a controlled mean of stress relieving whilst the casting has been 'teased' back to the desired geometry.
You may be able to research it, but possibly a long 'soak' in an oven, possibly followed by quenching might do the trick (certainly not the case with iron!) or a blasting process on the inside of the headset. Certainly over zealous industrial grit blasting distorts alloy parts as some of us have unfortunately witnessed.