Whatever a 350 has in it, it's not an electric kickdown. There are lockup 350's, and there are some 350's that know what gear they're in (for computers to know). There might also be some switch pitch 350's, although nobody ever told me that. I'm just speculating.
Whatever it is, you won't need it on a 70 Formula transmission. What you need there is 12 volts, through the switch, to the transmission.