It's a '56. The give-away is the vent (for cooling air) on the front fender below the chrome decoration, that was added for '56. The '55's didn't have them and it got pretty warm.
Also, the taillights of the '55, '56, and '57 T-Birds were the same as the Fairlane Vics' of the same years. I always look at the taillights.