I am new to modding 7 days but I have used mods in other games, How do the vehicles effect the game when installed, are they just loot able or can you drive them about and use them.
You probably just can't see their icons if you are looking in the Vehicles crafting skill section. The UI an only show so many. But if you open your inventory and search you can find the parts, and there it will show you what level you need.