How are the Widebody Cars put together?

Interested in widebody OEM kits for my v6 GT.

I’m sure cutting the body is involved in order to install.

I see there are screwing and adhesives required. And that’s the OEM kits.

I’m curious, how are the cars that come stock with Widebody from the factory, how are they installed?

If that’s just how the body is built, what’s stopping me from just swapping over the body from an OEM Widebody rather than cutting and adhering that comes with the OEM Kit?