I’m not sure about that. Hopefully someone else will chime in. I know you’re going to throw a bunch of codes which can be cleared once the transmission is reconnected but I have no experience with the 4l80. It will not start without the neutral safety switch telling the ECM it’s in neutral or park, I know that much. Not sure what other things it’s looking for before it gets the ok to start the engine.And once I get the oil pan and starter back on what all has to be connected for me to crank the engine to check for leaks...
I was going to try to leave the transmission disconnected so I can see if it still leaks