The new guy question...

[ImEvil1]

You could try to contact the agency to see if they have any old records of the cars (usually maintenance or property records) or see if they can tell you what method they used back then to surplus the cars and try to go that route (ie. an auction company). If you are lucky enough to find a VIN, Carfax and a number of other databases online can be helpful in your search (most are pay as you go).

Just remember that most states have privacy laws in place and you need to make sure you are in compliance with those when you attempt to make contact with someone who may now own of one these cars.