The reason I say this, is because you don't need to set-up a switching system to tell the PCM that you're in nuetral or park. (To use the '7427 PCM style correctly, you would need to use two relays to switch certain inputs to ground for proper "gear select" operation). I had some park and nuetral/low RPM issues when I was using the '7427 PCM with a non E-trans, and it seems that it would be because the PCM had no idea if the vehicle was in gear or not.
Wonder if I am going to have that issue with my sons 427 system in a manual truck and a manual $OE bin?