B494990 is diagram 1/044, there is a photo of this wagon in An Illustrated History of BR Wagons, it is unfitted 2 shoe Morton braked with metalwork painted grey and unpainted planking, with split spoked wheels.
M424330 is LMS diagram 2150, there is a photo in An Illustrated History of LMS Wagons vol 1 of M424333 it is unfitted 2 shoe Morton braked with metalwork painted LMS bauxite and unpainted planking, with 3 hole disk wheels
So it looks like Dapol are using the correct underframe for the numbers chosen but quoting the wrong diagrams in the description