Mercedes 280ge W460 Fuel leak near filter. What part do I need please?

The design of the w460's tank and exhaust system left a lot to be desired. Exhausts were routed over the top of the steel fuel tank, this required protection from heat and came in the form of [I presume asbestos] cladding. This cladding holds water and perhaps as a consequence of said moisture and the heating cooling cycle from the adjacent exhaust created perfect conditions for corrosion. Rust was top down and usually included all the pipe connections to the pump and filter. Best to take the tank off, secure it from falling via the access panel in the centre of the boot floor and loosen off the steel straps which as mentioned above are probably rotten too. Take great care not to get petrol into your eyes or ears when carrying out this task

I think you're right with some kind of foil backing, its been a long while since I had a w460 but the pleasures of petrol in my ear is a pain never forgotten. 

Only when the tank is dropped and inspected can you really tell what remedial work is required, corrosion of the tank itself is much more difficult to fix for a petrol tank than for a diesel because of the explosion risk when welding but feeding exhaust gas in might work, if the tank hasn't corroded from the top don't assume all is well, as the seams often leak, and its quite common for the owner to be unaware of the extent of the problem especially if they don't brim the tank very often

When my 280GE was done the metals expert filled the tank with water to eliminate explosion risk.  The main leak points were at the filler necks (plural as accessory tanks present) where water and dirt had been trapped between the rubber hoses and the metal causing several tiny holes.  Glass fibre chopped strand mat in multiple layers stitched together with s/s wire, then a piece of heavy duty aluminium foil from one of those disposable charcoal barbecue trays on top has made a good insulation layer over the tank where the exhaust pipe goes.  If you are giving the tank to someone else to fix, you are best to remove the fuel tank fill sender gauge as all the movement of the tank turning it on its side, upside down etc, without the damping effect of fluid within it will send the float up and down etc and the thin wire in the gauge will probably break as it's quite fragile.  Replace the protection plate over the pump on the front of the tank using some stainless bolts would be another tip learned from experience and will speed up access to the pump in the future.

agree the problem is gone for good but need to add the cost of re routing the exhaust, which is a good idea anyway even if you chose to repair your steel tank, as the convoluted rout it takes of the fuel tank is bonkers

Just use a suitable bolt or a nut with some scrap welded onto it.  Here's one I made earlier.