It's the material thats important , the original Vincent item was made of a specific grade of Aluminium made by the company Birmabright. There is an equivalent available today and Landrover (proper ones , not Disco or Range Rover rubbish !!) bodies are made from it.
Unless someone has got their act together do not be surprised if they do not fit. For years they have had too small a radius both across and along the guards and without using spacers they will not fit properly. There was some discussion on this forum some time ago about some of us getting off our rears and making the correct radii forming rollers but at the time this was squashed as we were informed that it was all in hand. Good luck but if they do not fit then my attitude is that they should be sent back to the supplier and that they, the supplier, should pay the expenses for supplying goods unfit for purpose.