Are these hubs with separate brake drums fitted? Most standard hubs & brakes these days use a 1-piece hub-drum. The boss dia of the hubs on my box trailer (no brakes) are 55 mm dia at their outer end which is 35 mm from the flange, then a smaller dia cap. If a drum was fitted to these hubs then a D3 alloy would fit. The hub's boss dia tapers smaller from a larger dia at the flange which is not necessarily the same as how a hub-drum is made.

