Just purchased a 74 z28, in my wife's family from New. In the engine compartment, driver side, appears to be a switch of some kind that mounts to an orange plastic retainer attached to inner fender. Any ideas what this is for? Previous owner cut the wires and inserted a fuse. Hatchet job!
just looked again, it says "START" on it and has a rubber covered button.

 

Sounds like they set up a remote starter switch under the hood,could be used for a variety of reasons like valve adjusting,distributor adjustments,compression testing etc.
They make a hand held switch with a jumper for attaching to the solenoid for such things,I still have one somewhere I used for adjusting the solid lifters on my old '69 Camaro.
May have had starter switch issues and used it for a fail safe? Hard to say.

 

Pictures

 

Amazing. Looking thru owners manual I see a picture showing the "starter interlock override button". For the stupid 1974 system under the seat that makes you click the seat belt before starting.