On my W114 chassis, I place the jack stands on the "frame" just to the rear of the front suspension, and place a pair of stands under the rear control arms.

This allows the stands to adjust to any floor irregularity, if the floor is off level.

Jim

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14 E250 BlueTEC black. 45k miles
95 E320 Cabriolet Emerald green 66k miles
94 E320 Cabriolet Emerald green 152k miles
85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles