What a brilliant idea to swap that motor into a Dart!
I'm planning to swap one of those motors as well, but just to an older Jeep, not a A body. Did you find out if the speed input was neccessary for the PCM to work properly?
I was looking a bit more into a speed signal and wonder if this would work to translate the Ford Speed sensor on my T5 to the Chrysler's ABS module so "mph" gets on the CAN bus?
Dakota Digital SGI-5E
The SGI-5E is used as either a signal multiplier (up to 16X) or signal divider (up to 125X), making this unit extremely flexible for almost any application. While the SGI-5E is intended to correct only the signal feeding the electronic speedometer, in many cases where a speed signal is shared or on a databus, the SGI-5E can instead correct the signal feeding the engine and transmission computers.