There are alot of little revisions on the dash for the 97-02 version. So if you get the 96 dash core, you will also need the upper dash( the part with the defroster vent) as well. Your 98 upper dash will not work with the 96 core, as GM changed the contour of the dash core on the Firebirds and Camaros in 97. All the other important stuff like the gauge cluster, radio, hvac controls ect will bolt right up from your 98 Camaro dash. And yes the 96 core will bolt right into the 97-02 cars.
Here is the Trans Am/Camaro 97-02 style
Heres the Trans Am 93-96 style. Notice the contour around the defroster is different.