[Francesco]

Oh well a lot of informations finally. Ok Bob first. The nut is exactly 3" measured with a caliper, the Dodge hub nut wrench is too small for this job. Also it is a six point nut. For what it concerns the "bush way" well, that's exactly what I did to disassemble the axle! After all it is not so common to have a 3" spanner in the box! I also figured out to thread two holes in the nut, put a bolt in them and use a bar to turn the nuts. The main problem is, in my opinion, that you have not only to turn the nuts, they have to fit the bearing to a correct measurement and that's not easy using a hammer and a chisel. So (thanks to Bob!) I would prefer finding out the correct spanner and do the setting correctly.
There are some spanners available here in Italy, but they are all six point nuts. I'd finally prefer to find one "on the counter" and the last option I'll make one myself.