Steve,
I doubt of the Jim Carter or Classic Parts wiring harnesses come with the multi-lead wiring strip/ribbon that goes in the steering column (that wiring comes with the signal-switch that goes inside the cup under the steering wheel).
Both vendors supply extra wiring for signals, because most people use after-market signals, not the optional/accessory GM signal assembly.
The Shop Manual would not show installation information for options/accessories.
Here is a link to 1954
GM optional signal installation and wiring for a Suburban. The wiring for other trucks in 54/55st would be the same.
