I looked through my files and couldn't find my old test results. However, depending where you are the CA test may be a dyno test (it is where I live) so the results will probably not be directly comparable.
That being said, from memory 537ppm NOx seems *really* high. Generally when the cat goes the NOx is the first to go, so it *may* be time for a new cat. But don't quote me on that until you get some better results.
Get the car in state and find a smog shop that will do a pre-test for you. That'll at least let you know where you're at.
1987 Milano Gold
1963 Giulia Spider (1750 engine)