I thought they had century on the sides too, but both cars are very similar. All regals had panels on the lower door and rockers. Those are century hubcaps, and the regal bumper comes down a little lower
Most centurys had wide door moldings, but that changed around 2003. The fascia is definately Century and not Regal. The chrome beltline molding on the fascia is would be about ½ way down to match the rocker cladding on the Regal.