74 Dart 360 Sport

Pretty sure you will need an aftermarket controller from Sound German Automotive. HPTuner makes it sound like you are going to try and use the OEM stuff and as far as I know that isn't possible without the G3 PCM to go with it, if at all.
Yeah will need both supposedly you can tune the with HPtuner to change the actual shift points. The sga is not programmable I read less that has changed.