How do i make a addon car like Panier 250?

[Slequer]

So I like making low poly cars for GTA SA and I had the idea to make cars for another game to give it a change.

I decided to try it on my summer car and I saw the new car addon Panier 250 but I cant find any tutorial on how to make a mod similar to it.

If anyone has experience with this type of mod you could help me with that?

 

Here this is the car im currently working on: