The correct tire size should be 6:70 x 15 and if you use whitewalls the correct white wall width is 2 1/2 approx. 1954 was the first year that the industry went to the narrower white wall width and got away from the old 4 1/4" that was used in the earlier K-F years from 1947 thru 1953. The 2 1/2" whitewall was used up to about 1962 when the industry again changed the whitewall width to a very narrow one.