W123 200e 1978 change final ratio

[dmaglione]

Hello everyone, my mercedes W123 2003 1978 94hp automatic has the final ratio 1:3,92.
driving at 100 km/h the engine rauns around 3400 rpm.
I want to change the final ratio using one of those final ratio:

- 3.69 from All 240D
-3.46 from All 300 non-turbo
- 3.07 from 300 turbo to 1984
- 2.88 from 300 turbo 85
- 3.69 from All 230 and 250

The car is driven 90% on highway and I don't know exactly witch one could be right for my mercedes.
Any suggestion please?