Not exactly as I was looking for.
I was after the 4.11 to take some load off the clutch. I also run 195/60 R14 tyres.
A few more measurements on the housing- diff centure bolt holes measure 195mm across centures and axle tubes measure 60- 65mm .
Thanx for the help so far.

The H165 diferential in 3.7 to 1 ratio was the original fitment in the Datsun 910 Bluebird poverty pack four door sedan when fitted with the four speed manual trans.
This applies to series one cars, & probably series two as well.
Five speed or automatic models got the 3.9 to 1 ratio.
There may have been other models that used it too, but i don't know of them.

3.7 is a hybrid...good find.

The 3.7 will be a perfect match for worked an A-series for the street. I wanted to put one of those with my CA18DET, but after the work I'd end up breaking it sooner or later.

The id for an H165 is that the centre is held in with bolts. not nuts with studs on the diff.

The 3.7 is a low volume Bluebird diff centre. Not as common as the 3.9 centre.

I picked up a " ute " diff to replace the current ( screamer!) i have under the rear now. After going through the info on the site I'm a little confused.
After pulling down the diff I just bought , it turns out to be a 3.7:1 ratio and not a 4.11:1 as expected.
The ring gear measures 165mm and axles are 26mm+-
is this the standard H165 from the 1200 ute or do I have some what of a hybrid?
The diff came out of a 1980 1200 4 speed ? ute but weather this is the original diff or not , I can't be sure.
Are there any other distinguishing features to ID a ute diff?
I currently have a " keep me on the road " diff under the rear at the moment- 120y I think?