Look in the GameData/Vehicles/[CLASS] folder.
There are the teams and you can just copy/paste a folder and change stuff accordingly.
For information on how the filenaming works and what to change in the .veh file, look
in the .txt files that come with the templates provided by Reiza.
If you create a new team with 2 new drivers (or just one) and assign them numbers
that are not used yet, then you will be fine.
I think the documentation that comes with the templates is really solid.