I have installed a 300TDT Radiator in my 280TE. Its a little wider, but fits fine. My car struggled to get to normal operating temp., even in the summer with this bigger Radiator in Seattle area. The 300TDT Shroud encloses the Fan more then a typical W123 Shroud.
I have an extra original W123/ M110 Radiator, but probably expensive to ship

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83 280TE- 5 spd, 16.5mm rear sway
85 280SL- 15" Bundts, 5 spd