Replacing all tanks with cars is very easy.
All you have to do is open the
ObjectSpawnTemplates.con for the map you want to mod in whatever mode you want ( CTF, Conquest, SinglePlayer or TDM ) then look for the ObjectSpawner that spawns the tanks.
Usually they look like this ;
ObjectTemplate.create ObjectSpawner lighttankspawner
ObjectTemplate.setObjectTemplate 2 sherman
ObjectTemplate.setObjectTemplate 1 panzeriv
ObjectTemplate.create ObjectSpawner heavytankspawner
ObjectTemplate.setObjectTemplate 2 T34-85
ObjectTemplate.setObjectTemplate 1 T34-85
ObjectTemplate.create ObjectSpawner ArtillerySpawner
ObjectTemplate.setObjectTemplate 2 sexton
ObjectTemplate.setObjectTemplate 1 sexton
Then all you have to do is replace the tanks with whatever car you want such as the willy, lynx, BlackMedal or Kubelwagen.
Here is what it would look like with cars instead of tanks.
ObjectTemplate.create ObjectSpawner lighttankspawner
ObjectTemplate.setObjectTemplate 2
willyObjectTemplate.setObjectTemplate 1
BlackMedalObjectTemplate.create ObjectSpawner heavytankspawner
ObjectTemplate.setObjectTemplate 2
LynxObjectTemplate.setObjectTemplate 1
KubelwagenObjectTemplate.create ObjectSpawner ArtillerySpawner
ObjectTemplate.setObjectTemplate 2
LynxObjectTemplate.setObjectTemplate 1
KubelwagenThen just repack your map and you will see cars spawning where the tanks used to be.