I followed the directions posted for a 300D and I, too, could not figure out a way to remove the first aid box as easily as everyone posted. I then learned that if you remove the backseat you will find the access you need for the fuel sender.

This is one of those times when directions for the 300D do not apply to us with the 300SD. Check out this thread I started some time ago with pics.
http://www.peachparts.com/shopforum/showthread.php?t=176522

I hope it helps

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Pictures of the MB: http://s230.photobucket.com/albums/ee41/EricandRobyn/1981%20Mercedes/

1981 300 SD with a Goldenrod water block and Injetor line heaters. EGR is missing

1999 F-350 with HP X-over, Dahl 100 Fuel Filter, Coolant by-pass filter, CCV mod, Tymar intake.

Both on single tank WVO blend