FiveM Modding Tutorial
This will teach you how to make ANY car into an add-on car, regardless if it was supposed to replace a car or not. This is a good choice for people who wish to keep all the original cars of the game while having their favorite cars installed. Also this is a good way to make your car customizable, so you can make any edits you want to it, whether you want to make a super tank jeep that’s indestructible… Or you want to make your SUV stop tipping over by editing its handling entry.
I have a file that contains some basic instructions on how to do this, and also contains instructions on how to modify your car.
This is the example file with all the information/instructions:
Here is a list of websites that will help you find other bits of info on modifying cars:
I hope this provides a decent amount of useful information, like making ANY car have sirens and such.
I added more things in the handling.meta and vehicles.meta files. Now you can see how to add weapons to vehicles, but ONLY if the vehicle model supports vehicle weapons.
I added a file that gives a small handful of weapon hashes that can be used for vehicle weapons, all of them I had proven works well with armed vehicles. This hash list gives a brief description of each of the proven weapon hashes.
Added a new weapon hash to the weapon hash info document ( VEHICLE_WEAPON_TURRET_INSURGENT ), and sorted it alphabetically.
Original source: https://forum.cfx.re/t/how-to-create-modify-your-own-add-on-car/15217