The 1958 to 1973 catalogs didn't give that type of information. I assume something like the Guild EA-610L or EA-610M flatwound strings. But also watch out what type of bridge you have on your guitar (compensated or uncompensated for G string) means if you need a wound or unwound G string. I believe the vintage EA-610 strings had a wound G string.
The Newark St. T-50 and others for instance ship with D'Addario EXL115 Nickel Wound, Medium (.011 - .049), which has a plain steel .018 G string.
Ralf