AMO standards weren't adopted until Feb 1968 and state that a bow's length is determined by measureing the string that braces it correctly (measured under tension) and adding 3". So a 64" bow should use a 61" string. The '59 Kodiak is pre-AMO standards though and the two 64" Kodiaks I've shot were both slightly different lengths, despite both being marked 64". Come to think of it, all three of my 1959 64" Bears need different length strings (Kodiak, KSpecial and Polar).
I'll measure my Kodiak's string when I get home tonight. That should give youa good starting point.