Just added the only two other pics I have of this little rocket
I can only suggest that you send an email for the attention of Phil Ward at Auto Italia magazine in the UK - he'd know more about it (perhaps the car has been featured in an issue already, I don't buy every one any more). The other potential source of help regarding specific parts would be
Middle Barton Garage, they might be able to tell you where that cylinder head came from. Their site is also worth exploring if you don't know it - some fantastic cars in the gallery (check out the RHD 750 Bialbero at the end!).
Alex.