How to use any car in Custom Championship or FreePlay mode?

[Beef36]

I recently purchased Dirt Rally 2.0 GOTY which includes the Colin McRae pack.

I'd like to use the older Subaru Impreza 2001 in custom championship and freeplay modes, however in both modes the selection of cars does not include "4WD Up to 2000cc" class and probably some other classes too.

How can access all cars in both custom championship and freeplay modes?

[turtleCZ]

It must be there, it's the only modes I play.

[solargazr]

All cars are available in custom championships.