My '73 caprice has no electrical hook ups on it anywhere SBC 400, TH400. Absolutely no electrical hooks on the carb. The kickdown is operated solely by vacuum pressure. GM may have, perhaps in later models made some provisions for some electrical downshifts and I know that there is much electrical in newer model OD trans, but I have been thru a couple of early TH400's and not seen this. I could be wrong, but I'm pretty sure.