I put my '82 240D's old Group 49 battery in my '72 W114 SOHC 250C and it fit just fine. I believe the SOHC gas models have the same oversize battery tray as the diesel models.
With your car, there's no problem with the voltage, but the twin-cam 280 engine is bulkier, with the intake on the driver's side. The battery tray on yours may be smaller or located different.

Happy Motoring, Mark

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DrDKW