Jimmi,
Do you have a trim strip on the top edge of the dash, right under the bottom edge of the windshield? If you do, squirt penetrating oil around the screws and let them soak a day or two. Then, remove the screws and remove the trim strip (it is called the defroster deflector by some people). You'll then see the two slots for the "outlets". As I recall, in 1954/55 the two vent outlets are different from those used in earlier Advance-Design years. Also, each vent outlet haa a screw attachment on one side and a clip attachment on the other side (I dimly recall).
If you want to see photos, please ask. If someone does not post them by this weekend, I will.
