Tried to replace the manual fuel pump, but it doesn't fit?!?

('79 300TD; W123)
Tonight I tried to replace my manual fuel pump 'cause the original one is leaking. I went to the dealer, pointed at the picture, and got the
item ordered.
I went back today, 'cause I figured I needed a gasket or something. The dealer told me, "oh it comes with what you need". Ok. Back home I look at it carefully, and no, there's no "seal ring" in the package.
Anyway, I pop the old manual pump out (not a lot of room in there for a wrench of the appropriate size, eh?), pull the seal ring off the old pump, and hmm interesting, it doesn't fit on the new pump. Like, the OD of the seal ring is the OD of the pump minus the threads. So, obviously, the new pump did not get installed as it would not fit in the hole.
I'm wondering then a few things: might I have a pump from a different car? It looks like the pictures over here:
http://www.detali.ru/cat/oem_mb2.asp?TP=1&F 3190&Ma7%2E912&GAr2%2E118405&GMq6%2E005++++++++++++++717%2E400&CT=M&cat3&SID&SGR5&SGN
If I do in fact have the original equipment on my car, is there any precedent for Mercedes giving out the wrong parts? The part number seems to match; the packaging I have says A 000 090 88 50, and the above site lists two: A0000900050 and    0000908850 (am I'm guessing correctly that the second column means, "superceded by"?).
The fact that the new one doesn't have the seal ring is suspicious, but it seems odd that MB would have the wrong part in the bag. There's no way the part I have will fit. Any thoughts?
thanks, -tom!
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Give them your VIN number and they will get the right part for your car. Seals NEVER comes with the part... always separate.
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You also should provide the engine number to make sure. I found out the hard way when I was replacing the serpentine belt, that my 95 SL 320 really has a S 320 engine installed. The dealer parts department told me that this kind of thing happens frequently Peter

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Tiger wrote:

Gave them the VIN, and the diagram of the part at the dealer, as well as with the link I provided, indicates that the seal does come with the part. It's a copper (or brass?) ring. (Note that part number 344 indicates that it includes 347.)
-tom!
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Tom Plunket wrote:

I was looking at this pump, pondering returning it to the dealer, when I noticed a brass ring in the middle of the assembly. Giving it a good twist, it turns out that the pump I got had an adapter on it for some other fuel system, but taking that adapter off gave me all the bits I needed. Five minutes of wrenching and it was installed completely. Not really sure how tight to make it in there, a 17mm wrench hasn't got a lot of space to maneuver.
Very odd IMO, but cunning at the same time. ;)
-tom!
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