Wow,you are right, I just looked in my #5 mower book dated 1950 and it does NOT show the cable lift option. I looked in another #5 mower book dated 1956 and it DOES show the cable lift option.
I have the cable lift option on my mower along with the parts for Hydraulic cylinder lift or foot lift options.
Here's a picture of the page showing the cable lift option. If you look close you can see the two pulleys. Also the special lever on the mower end of the cable. There are also two metal straps on the mower end of the cable, they have several sets of holes to adjust the length of the cable, and a offset bend in them. Those details you can not see in this picture.
I think I've got an extra copy of this later edition of the #5 mower book if anyone is interested.