It seems there is only one number for the 16v cylinderhead, which is 46822135. There are versions with and without the addition "01T".
What exactly is the difference is not clear, but it is abvious there are two valve stem diameters, 5 and 6mm. Normally 5mm should flow a little better because of the larger flow area, however it looks both versions are used in euro 4 engines. Not sure about euro 3.
Rumours about euro 3 heads having bigger ports and flowing "much" better than euro 4, I don't believe as I think there's no difference. If anyone has measurements that prove otherwise, please share.
147 JTDm 16v - GTB2060v - 329 hp/578 Nm