They look at the capacity of the motor fitted to the vehicle you are trying to pass, so 1.5 or 1.6 EG, max motor 1.725ltr or 1.84ltr if fitted with a 1.6, so no k20 allowed without engineering it.

Dc2 being a B18 and 1.8, 2.07 ltrs allowable so K20 no prob.