I certainly wouldn't get Ford to rebuild a cossie head.

You can get a complete head from 300 to 2000 depending on spec and then the old head still has a value, if it were me I would rebuild to a better spec or buy a replacement. There was a high spec one on here for 300 which had a slight crack with decent test report, 900 on that would give a repaired high spec head. Look for Gary at RS cosworth breakers on here from Portsmouth.

https://passionford.com/forum/ford-r...ine-parts.html