Exact match is 81-84 300SD.

If you can find an 85, use your torque converter and it will work fine.

You can use a W123 300D turbo trans but you need to swap the tailshaft.

W126 cars use an electronic speedo feed, W123 use mechanical cable.

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