Haven't rebuilt mine yet, but I suspect those vanes in the rotor have to be oriented correctly; IE, with the rounded, machined edge outward, to face the oval-shaped 'pump chamber'. From the appearance of the machining on mine, I wouldn't think the pump would work correctly - if at all - if the more 'squared' edge of these vanes were oriented outward...

I'll have more experience with this in a day or so...
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Update: this project is now done, and the power steering is better than it's ever been. One gotcha: I made the mistake, initially, of not fully compressing the three internal elements of the pump 'core': front plate, ovoid pump 'chamber' and the backing plate. Correct assembly can be tested by checking the back-and-forth play in the shaft; there should only be less than a 1/16th inch from the shaft-rotor play, and no more.

I had not compressed these parts fully, and the loading spring was not adequate to push them together once assembled. Result? No pump pressure! Easy to fix with a correct reassembly.

Some part numbers; hopefully this will help someone out there (this is all for a W126, an '83 300SD):

Pump details: ZahnradFabrik Friedrichshafen A.G. (Schwab. Gmund)
Mercedes #: 126 460 1480 type: 767 2900 446
Gasket Kit: A 000 586 84 46
(2 O rings, one Aluminum washer for pressure valve cover)
Front Shaft Seal: A 018 997 60 47
Filter: A 000 466 21 04

Lou