The car numbers are just that, car numbers. Nothing special about them per se expect that Car 5-0 is usually the Sgt and/or supervisor.
Most of the marked cars are in the 40-49 range. Since they don't have the numbers on them. I am not sure what the unmarked car numbers are.
In addition, there are some civilian trucks with PD marking on them for streetlight repair ect. They tend to be in the 50-70 range.
I think animal control may be 79, but I could be wrong, that may have been someone elses ACO.