Fuel pump on 520i 1992. M50

[baksa]

Few weeks ago my car couldn't start and after a while I figured that fuel pump is dead and it doesn't deliver fuel to engine.
We removed it from tank and tried to start it with direct electricity - no go, dead totaly. Whole day I tried to find a new pump, it was saturday, and I managed to find one that fits into metal tank. For my surprise I realised that my tank is plastic (I didn't know that???). New pump fits into tank but it is an inch hihger than the old one so it means that my fuel has to stay above certain amount or pump will die again because it needs fuel all the time.
The old pump - we tried it again with direct electricity and suddenly it started to work.
My question is - anybody knows the different serial numbers for pumps (for metal and plastic tank) so I could get the real one, and your advice - is it clever to clean up the old one and put it back?

[Dr. evil]

i don't think that it's a very good idea to use the old one. When mine went out it only worked off and on, the injectors like to have alot of pressure.

as for the plastic tank, never seen one

[t_marat]

I have a plastic tank, EURO model. As far as I know cars exported to USA had metal tanks. The fuel pumps for them are different.

My fuel pump also died last year. Found some on Ebay.de, can't remember with what terms I did the search. Eventually bought a used one from another BMW locally.