Other differences (from what is listed by others in the other thread):
GMC horn "button" on the steering wheel is different from the button on a '54 Chevrolet truck (an obvious difference).
The speaker for the GMC radio mounts in the headliner and not on top of the radio (and thus there is no problem mounting an after-market electric wiper motor in the '54 GMC with a stock GMC radio).
The '54 GMC Hydra-Matic gear/drive selector on the column is different.
