Still haven't heard back from Marti....or anyone else. I did try and track down a fleet guy in the Houston area (long since retired), but I'm still trying to run that to ground, also. So basically, no new info.
However, I did stumble across this old scan from one of the police vehicle books I apparently have. I will start research on the plate tomorrow AM. Oddly enough, I posted this here in 2008 and didn't remember it.