I have two Monteros with swapped engines to 4D56TDI. I got them with the 4D56 engines. Is there a way to find out the year of manufacture of these engines? I need to order new thermostat, but I want to make sure I get the correct part. I did some search in the forum and it looks like the part number for the thermostat is MD997606. This seem to be the part for 4d56 from 82-89, the part number seem to be different for the 4D56 from 1990+. Any help will be appreciated. Thanks in advance!