The Turbo 375 an 400's all used an electric solenoid for full throttle kickdown. It's been a while... I believe the carbs had a switch that sent voltage to the connector on the trans at full throttle. Never hooked them up in the race cars. Just like a TH 350 uses a cable for full throttle kickdown, neither one affects normal shift points. You could hook up a momentary switch to send voltage when the carb hits full throttle only and get it to work, not too hard to do.