Rare cars you dont see anymore,

[powerandtorque]

As I understand it, to get a new registration, the bulk of the car must be new (including the chassis/monocoque) and a single major component may be used/reconditioned - often this is the engine or gearbox, which is I suspect how the Megablade above was done.

With a single-donor kit (Sierra based was the classic in the late 90's) if you use enough of the major parts from the donor car thus scoring enough points and have a new chassis/monocoque, you can get an age-related plate. As I understand, they really shouldn't be running around on the original registration/V5 from the original donor car.

It's all there on the DVLA website somewhere.