I would install an electric pump inline either below the tank or near the engine. They are cheap, reliable and depending on how you set if up can give you a performance boost. Most modern EFI gasoline pumps are overkill for ours cars. A diesel solenoid pump will do the job. It's also handy if you ever need to drain the tank or remove air bubbles from the system. On the w210/om606 the powerful lift pump tends to pull in air bubbles through various fuel line connections so adding some positive pressure near the tank aleviates that problem.
I'm using a Delphi fd0040 pump on my om603 and om606. It makes 12psi. I can switch it on manually or automatically over 2.5psi manifold pressure.
