No, with an exception.
It was an option on GN's...but...
Now the exception...In 1987 the demand for the GN's was so great that had to extend production.
GM then came down and stated that all GN's being produced during this extension WILL have certain mandatory items in the GN package and POSI was one of them.
I have a copy of the actual letter that they sent through the corporation stating as I described above.