Hi Button,
Are you wishing to repair a crosshead as well as Morgan_75?
Obviously without seeing yours it's difficult to say. If the centre of the crosshead is not distorted, it should not be too difficult to repair.
At risk of sounding repetitive, I'd call Terry and ask his advise and perhaps send some images. GEE make chassis for early cars and so will have all the measurements required.
Regards, David.