How do i convert a GTA V vehicle to a FiveM vehicle?

Right i was speaking to someone on these forums, and i asked them help for a “Physics validation failed for asset firetruk.yft”

so this has been happening to me a lot with the Ladder Trucks(ALL of them)so thats why i need this sorted.
he told me i would need to convert it so its made for FiveM, if so, how would i go about doing this??

This error occurs when the vehicle you’re trying to use, is bad. FiveM will automatically block bad vehicle models.

Even though there not bad… They worked fine before but now… there blocked.

If you ever got random crashes, then it was probably the vehicle model, which is why it was blocked.