601/2/3 pumps aren't rebuildable like the 616/7 pumps.

Pierburg is a good brand. If you get a pump from the dealer, chances are it'll have Pierburg markings. Don't assume that to mean it's the same pump! The Behr radiator you get from an MB dealer can be different from the Behr radiator you buy somewhere else. I understand Phil/FastLane sells Febi brand pumps made in Italy. There are [Chinese?] pumps on eBay for half of what a Pierburg pump costs. I don't know how good they are in the long haul. What other brands have you seen?

Sixto
87 300D