38E wrote:When my '62 was registered in England, it wore a rear plate that was cut to shape filled the whole space between the  plate lights. The numbers were stamped into the plate. I don't know where you could get that done these days, but it's an idea.
That would be impossible in Belgium: the rear plate is delivered by the fiscal authorities at a given format and are stamped with an official stamp. 
That holds for all cars, including oldies, with no exception.
Btw, the front plate does not have a stamp but you are supposed to have it with the same imposed format.
Departing from the regulatory plate means risking a heavy fine...