I think I forgot to tell anyone or never made a point of it so here goes. It doesnt provide the freeway ratio of 3.7 but it might help anyone else for an alternative for a 1K beef up.

I found a 1967 bluebird sedan and the diff came off quickly after I found that all the brackets are exactly the same as my 1000s. You might think so what but the bluebird had a H165 diff centre with alloy carrier and bigger drums and the best of all the exact same width as the 1000. So if you see one at the wreckers save the diff itll be a sadly lost item for a 1000 if you ever get one.

Ive been told that the alloy finned drums from the 240-260z are the perfect replacement for the cast iron ones.
The only thing is that I dont know if the axles would interchange, if its metric or imperial or anything else really.

Thats my 2 bob worth anyway as these diffs sat behind an L series type engine in the SSS version with 1.6 litre capacity and one tonne dry.