Can't help regards metal stitching but I can recommend
www.castironwelding.co.uk
I have no business connection to them but have just had a Mazda rotory centre plate welded there and it machined beautifully, cast will go rock hard if welded incorrectly but this machined as easily as the original material around it,
They are now welding a Bristol V8 inlet manifold for me that is cracked, so if you are totally stuck it would be worth getting in touch with them.
Steve