Your alternator should have a rating label on it. US cars had a couple different alternators on different 123 body cars. They usually were rated 55 or 65 amps. These actually were real POS alternators. They commonly only produced 50% of rated power at idle. If the A/C is on the blowers alone take 30amps or more. Many MB models through the eighties had the same problem.
They are now using alternators with outputs over 100amps and they get 90% of rating at idle.
The brush number from Bosch is either short # 11 011 or long number 1 127 014 011. We never replace just the brushes as they come attached to the regulator and with extra labor you might as well replace the regulator bruch holder.