According to the "LIBRARY" at Hamtramck-Historical

1963 b-body:
7.00 x 14 STANDARD
7.50 x 14 OPTIONAL (STANDARD Station Wagon)

Kelsey Tire sells a reproduction 7.50 x 14 with a 1" white wall
(7.78" section width, 27.68" diameter & 4.675" tread width)

Modern equivalent - 215/75/14 - probably the largest 14" tire you can find
(8.5" section width, 26.7" diameter & 6.2" tread width)
or
225/70/14 - (9.0" section width, 26.5" diameter & 6.7" tread width)