What you should know about park/neutral when doing an engine conversion with the LS1 PCM and automatic transmission...
Camaro/Firebird
This is the only vehicle I'm aware of with the traditional single wire park/neutral indicator. Ground the orange/black wire connected to BLUE PCM connector pin 34 to indicate park/neutral. This is how the PCM knows which commanded idle value to use.
Corvette and Truck
These vehicles use four wires to the PCM to determine selected gear from a switch mounted externally on the 4L60E/4L80E. Faking the park signal by applying ground to pins 32 and 34 may result in a long delay for the PCM to recognize gear change.
Calibration Choices
Determining a base calibration begins with crank resolution type (24x or 4x), throttle type (cable or electronic), and transmission type (4L60E or 4L80E). I've seen applications where the base calibration expected the gear select switch, but the transmission was not equipped.
Park/Neutral Calibration Options
A recent customer ran into this issue and was able to change the value for gear select switch to P/N only. Currently I don't think EFILive has this, but I'm sure a .CAX could be worked up by someone with the know-how.
A practical example would be an electronic throttle equipped engine with TH350/TH400 transmission.
Hope this helps.