Well, its pretty hard to give advice on used springs.
It gets even more difficult when you throw the variety of versions that can exist in european trim. MB really limits the options in the US.
Looking up springs for a 1980 240D and 280E brings some interesting considerations. The 240D has three springs available by chassis number and amount of special versions.
The springs are labeled: 1: Front spring; used with 0 to 2 special versions, 2: Front spring; used with A/C & 0 to 1 SA (special version), 3: Front spring; used with A/C & 2 SA.
The 280E has only one spring listed but comes with this description: Front spring; used with A/C & 3 SA.
The number for the 280E spring and the heaviest 240D spring are the same. Sooooo, if it were a US car with A/C the springs probably would be the same. The 280 would not be available in the US without A/C so there are not the spring varieties for it. This counting of accesories to determine springs has not been discussed in US service manuals since the early cars as the possibility of different versions does not exist.
My interpretation of this means that whichever car has A/C will probably have stiffer springs than one without. It also makes sense that a car with A/C also has other variants.
Bosch Master, ASE Master, L1
33 years MB technician