Today became the day for the replacement, unfortunately it gave me more troubles than expected...
The old bearings have probably been installed since 1964, which means they were completely stock, no matter what I did, only small pieces came off, instead of all of the bearing.
Finally my dad reminded me about the trick to weld the track of the bearing a few places to loosen the track. After that everything went quite smooth.
Out with the old bearings
In with the new bearings
Assemble of the cams