Between 1968 and 1971 there were some minor amendments that tidied things up a bit.
For example artic trailer lengths were increased from approx. 33 ft to 40 ft and this permitted 32 tons gvw on a 4 axle artic. It meant the end of the 5 axle artic for a few years until later gross weight increases.
A rigid six-wheeler gvw increased from 22 to 24 tons (basically 2 tons extra payload which helped the tipper men) and the rigid eight-wheeler gained the most increasing to 30 tons gross on a manageable wheelbase and outer axle spread.