I think it was moving the fuel tank behind the passenger seat from underneath (116->) where MB lost their trunk space. Amazingly pitiful is trunk space in 116's and 123's. And pontoon bathtub Benz were outrageous for having a trunk lid that closed at bumper level.

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'80 300SD/ w116
'79 240D 4-spd
'71 750cc Guzzi

previously owned:

'83 240D 4-spd
'77 280SEL 4-spd
'74 280/8
'72 250/8
'65 220Sb 4-spd
'63 220Sb 4-spd
'63 190c 4-spd
'61 220Sb 4-spd
'60 190b 4-spd