You could try a caravan dealer or repairer who may/should know the legal axle weights on your particular model.
When I converted to electric brakes on my old 1976 a few years van years ago I took it to Melbourne trailers and they said the original axle was not up to the actual weight of the van, and it only cost me $700 approx to replace the whole lot incl. axle, springs,brakes, fixed coupling, cables, wiring etc.
I was happy and satisfied that it was not only legal but also a lot safer and handled better as the original weight was marked as 1275kg, when it actually weighed 1425kg.and only had a 1200kg, rated axle.
I have no affiliation with Melb. trailers apart from being a very satisfied customer.