well I know with some pcms a case relearn is needed but it wouldn't start if that was the case
thought for a moment maybe having a different vin number on new engine might trigger the theft system but check the video and see if it helps
that parking switch lock is easily accessed bypassed
2002 Pontiac Grand Prix "Press Brake to shift from Park" switch fix - YouTube
this is a good breakdown of the same problem and the components
u can see the button he presses in on the new switch would be what you wanna toggle to see if this is the issue
