71 Dodge Dart Swinger in England

In the Uk if the vehicle is over 40 years old its road tax and inspection exempt. So my 58 GMC Apache, 68 VW camper and 71 Dart all road tax and MOT free, if they weren't i wouldn't be able to have them all on the road. However the 2000 Boxster and 99 Discovery arent tax free and that costs me about £600 per year for both