GTA5 vehicle mods come in two flavours with completely different behaviour:
Add-on
- Goes into dlcpacks and leaves the original cars alone
- Spawn it from the vehicle list in your trainer or the toolbox
- Uninstalls cleanly — the way to collect many cars
Replacement
- Overwrites one existing car (e.g. swap a super car for a Lamborghini)
- Only one replacement per car: if two mods replace the same vehicle the client flags a conflict
- Good when you only want one car changed
Vehicle packs
Dozens of cars in one go: expect longer installs, and more replacement conflicts.
Common problems
- Car will not spawn: wrong model name, or the mod is not enabled
- Crash on launch: two replacement packs hit the same car — disable one
- Invisible car: missing textures, common in old packs; reinstall or use a newer version
See also: Handling mod conflicts · Install guide