I got mixed up - for some reason I had the throttle cable in my head. The choke cable goes horizontally from the engine side of the carburetor to the choke arm. I found some decent pics in a
thread on another site. Keep in mind that these are pics from a chevy truck, but I think the GMC bracket and linkage is the same. Post #3 shows the throttle/choke bracket on the carb. with the choke cable running horizontal. The vertical part of the bracket is for the throttle cable. Post #6 shows a picture of how the other end of the choke cable runs through the choke linkage - they have crimped the wire, but you should really use a
cable stop.
The throttle cable installs in a similar manner, with the throttle wire running down vertically through the throttle linkage. It should also have a cable stop installed. Again, sorry for the mix-up.