If the cars are drivable (ie. they are actually locos), they should show up under "vehicles" in the Find Object menu.
If they are just scenery objects, they won't. However, if they are scenery, they will be listed in the kuid-table section of the config file. Manually deleting them from that list will not (I don't think) really delete them as dependencies of the route. You can remove them from the config file alright, but next time you load and save the route, the config file is rebuilt and those kuids will re-appear in the config list.
As Ahsan suggested, you can open the config in Notepad and use the Find menu to locate the kuids if they are in that 700-item list (you may have missed them in a manual search). If they are not there, but still visible on your map, then something is out of sync between the map and its config.
In that case, one way to really delete the cars is to remove their corresponding folders from the \World folder (in TRS2004 *) or whatever the equivalent of that is in TRS2006 or Classics. Then load the map again. The missing cars will cause a 'missing assets' warning to come up. In Surveyor, use the 'delete missing assets' menu, then save the map.
You can then put the cars kuid folders back into Trainz, but they won't re-appear in that map unless you deliberately choose to put them back.
* or use Trainzobjectz to list the map's dependencies, right-click on the car's kuids and elect to replace them with a non-existent kuid (F8 key).
