According to the LCOC Authenticity Manual (Which I am not lending to anyone!) The whitewalls were 3" from 1955 up to October 1956 and 2 3/8' thereafter.
Tires sizes were 8:00 x 15" Non A/C and 8:20 x 15" with A/C.
Domestic tires were 4 ply tubless bias ply, non belted. Export Models were 6 ply tubless bias ply, non belted.
Tires were Firestone unless otherwise DSO'd.