On today's big letter Goodyears the lettering is larger than that used on the original CSX cars--but as close as one can find--for that "period" look--unless you happen to find some original tires stuffed in someones barn for the last 30 some years
The original tires had Good,winged foot,Year in about 1-11/4 in tall letters , white. I had these same type tires on my '67 vette, when I bought it in '70.