Bottom one is possibly for a 300D, top one is for a 240D.

For the record, the 240D radiator on top works with A/C. I had my A/C working before my timing chain skipped and it kept the engine nice and cool at idle in 90° F outside temperature.

Probably not enough cooling capacity for a 300D, but I don't know for sure.

__________________
Milan Brown 1979 240D, rebuilt OM617.952 turbo diesel, rebuilt 722.315 transmission - engine spun a rod bearing

1979 300SD, ~90k original miles, all stock