are u sure the mondeo wheels arn't +40 and the old focus wheels -40, thats a 3ish inch differents, may be the other way round, but if the wheel mounting is dead centre of the wheel, then offset is 0, then depending weather u need to bring the wheel in or push it out it goes up or down in mm, so a difference between + and - 40mm is 80mm, 75mm = 3 inches, the profile shouldn't matter as it should move inside the arch and never touch.