I'm was looking at Corvette Central for this solenoid, but the part they list is from 77 to 82, excluding 1978. I called them to ask if they had one for the 78, but they say it has been discontinued. They were unable to tell me what the difference was. Does anyone know?

 

Welcome to the forum. Best thing I can offer would be to get one of the available idle solenoids and see if it could be modified to fit a 78. I'm not sure why the 78 would be any different than any of the others.