What makes you think it is a front diff ? As far as I know they are both the same, some early ones have a filler and some do not. Think very seriously about fitting 3.54 diffs I tried them and it was awful the driveability was ruined, constantly dropping to third gear and little or no noticeable economy change or speed at the top end. Mine is a 2.25 diesel petrol or TDI may pull taller diffs a lot better.