We were delivered a Rolls-Royce radiator to cure an overheating problem When we examined the radiator we found the 33% of the tubes had been blanked off to accommodate the angled corners of the radiator.
The original core would have been a film core which allows angle corners to be built into that type of construction, unlike the more modern square cores
http://www.coolexperts.co.uk/motor-vehicle/recores/film-type-ribbon-cores/
A stepped core was manufactured in the modern horizontal tube construction, with extra brass on the edges to allow us to shape the corners and reinstate the whole core for use in cooling.