Yes well Gary . I have rebuilt a couple of Meters type M mills .In both cases I have poured and fitted new white metal bushes . In one case the hub was badly worn ,that is the bore was way oversize and out of round , as the fan had been running and wearing the bore of the hub. The repair in this case was to bore out the hub and fit a new steel bush that had been machined for an interference fit into the cast iron hub, I had to be careful as there was not much metal and I did not want to split the hub as I pressed in the steel bush. I had pushed a 1/4 inch broach through and produced a new key way in this new steel bush . With regards to the shaft to bearing clearance ,the shaft was a new one machined to a diam of ! inch and when assembled would have what would be classified a ''Running or sliding Clearance fit''. The oil recommended is what they called''Wind Mill Oil'' It was claimed that it did not froth due to the meshing of the gears. I have used straight SAE oil , cheap Woolies brand and it does the job.
I have never rebuilt a Southern Cross mill but would assume there are much the same details .
If your mill is what is known as the Seneschal then it has a different oil system ,ie a hand pump at the base of the tower which enables you to top up the oil reservoir . Alternatively Your mill may be the Southern Cross ''H ''Pattern which has double enclosed gears ,the babbitt metal bushes are flooded when the mill is in motion I would say that the standard ''Running or Clearance'' fit would apply.
I have had old farming individuals tell me that Nylon makes a good bearing bush ,maybe but I prefer the white metal , my thoughts are that Nylon could in fact wear the shaft.
Hope I have helped .