When we had a Pegasus 462 (12 years ago!) it too was plated something like 1376kg but uprated it was 1490kg and the axle was labelled 1500kg. No manufacturer would build an axle to weight capability and then expect it to be run at that. There has to be some headroom - I would have though at least 10-15% - else how can the axle handle all of the bumps on the road especially with our current pothole situation!!
The maximum permissible axle load that the manufacturer specifies already includes a safety margin to cope with road conditions.
But, it's the axle load limit displayed on the weight plate that also shows the MTPLM that counts, not the axle rating displayed on a plate attached to the axle itself.