Curt
Locate the starter just left of the battery. Follow the wire from the bottom of the solenoid leading to the circuit breaker. You will find the button.
Bruce
The 51-52 Truck was still using the grounding starter button. Our you sure it switched to a power button in 53?
The 48-52 manual has the starter button schematic in a different part of the shop manual. Either the starter section or ignition. I don't have the manual in front of me.