I drove my 123 car this weekend to compare the rides between the two. Gotta say, its a better driving car until about 50mph than the 126. Goes around corners faster, feels more solid, and has a better turning radius (or it seems to).

After 60mph, the 123 car runs out of power (non turbo) which tends to make it feel maxed out.

I also prefer the big steering wheel in the 123 car.

Again, bit cars have rebuilt suspensions and recent shocks all around.

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'90 300SE 298k
-300K and it gets put into retirement.
'80 300D 255k Purchased new by family in 1980.

Had a:
1973 220 (gas)
1980 300SD
1992 400E