1. Factory service bulletins for the 904 and for the 587 motor. I do not know if this is the complete list for 904 related service bulletins.
2. 904 factory technical bulletins 2 through 9. Have not translated technical bulletin 1 yet.
3. 904 factory alignment information in English and German.
4. Weber carb info for 46 IDA and 48 IDA. Neither are original for a 904 however the 46IDA came into use in the 1960s after the 46 IDM became hard to get. The 48 IDA is used today for vintage racing 904 motors, but is too large for a 587/1 street motor unless dot 2 or dot 3 intake cams are used in conjunction with a larger intake valve as found on the 587/2 or 587/3 motors.
Many thanks to Tim Kyuser for most of this information. The original German language technical bulletins may be found in the Barth 904 book.
It is interesting to note the amount of experimentation the factory went through in some areas. The clearest is the evolution of the air ducting on the rear quarters behind the doors. Technical Bulletin 3 proposed one air routing and then it is revised in Bulletin 7.
If you have detailed questions, best to ask Tim Kyuser, Jacques LeFriant, Dennis Frick or Jeff Adams.