Don't know the ratio for the euro, but it should be stamped into the rear of the housing. Look on the rear below the rear cover on the drivers side.

I have considered changing my 3.07 in a 80 300SD to a 2.88 for better cruising rpm.

__________________
1980 300SD Manganese Brown Metallic Clearcoat 248k
1979 300SD White 148 k
1984 300D Silver project car for daughter
1982 300D wrecked
1980 300SD 310K not running