While looking for some wire data, I came across this website today (the tag line is 'Hard to find stuff for cool vintage audio'):-
http://www.vintagewindings.com/
and also this book - 1958 Belden Wire Data
http://www.vintagewindings.com/gen%2...gWire-1958.pdf - 91Mb download.
I didn't dig any deeper into the website as the book was of most interest to me.