Don't know if the stock wiring harness will fit (length of wires being either too long or too short), but the ECU will also control a 4L80e. Modern cars have a separate TCU to control the tranny; tying the ECU and the TCU and the three other computers in the car all together controlled by the central computer. This complicates the wiring and you won't need all of the computers that a stock car has (unless you are adding air bags for collision, as well as the anti skid brakes, emission control, and climate control).
Cars I built where minimalised (stock harness disassembled and the extra circuits cut out). I used an aftermarket FAST ECU, and a TCI TCU that was also fully programmable. I cut the the cross-member and boxed it to clear the Camaro oil pan that donated the motor.