Engine VIN number is in the 8th position of the VIN (quick google lookup here)
3 is correct for the type you mention (zetec)
Different number there should indicate a different engine in the car, so in the vast majority of cases that number will match (very few complete swaps out there).
Engines didn't change when installed in different body styles, but you can find detail differences in the externals, particularly in sensors/plugs between cars.