There used to be photos of a tool made from an aluminum strap that could release a hood with broken cable.
One of the aftermarket Corvette suppliers (sorry I can't remember which one) had a tool for that purpose.
1973 L-82 4 spd
I have only seen one for C-4 Vettes. I also have a 92.
I googled C3 hood release tool and got all manner of YouTube videos and Forum posts. I couldn't find a specific tool but found others that had described things that they had made.
1973 L-82 4 spd