Some of the Walmart Everstart batteries have been pretty highly rated in Consumer Reports, and the price for the Everstart group-49 battery to fit the W123 diesels is attractive - BUT...
According to the date-stickers on the two group-49 Everstarts I recently checked in my local South Alexandria - Hybla Valley Walmart, they had been on the shelf for about two years!
I imagine the group-49 size isn't a real hot-seller most places. So check the date-stickers on whatever battery you pick.

Happy Motoring, Mark

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DrDKW