Quote:As per the other thread that you started on this subject, it looks like your car came with a H145 differential from new. [H= Nissanspeak for 'diff'. & the number after it is the diameter of the ring gear in mm]
Your axle housing will take the later H150 diff with a spacer [if required] The H150 diffs come in 3.9, 3.7 & 3.54 to 1 ratio.
The larger H165 differential is usually found under models that came with the L series engines as well as many 1200 utes.
The H165 differential will not fit the H145 or H150 housings.
The whole H165 rear axle assembly from a 1200 ute is the most practical upgrade for 1200's & 120Y's but the original diff in it is 4.11 to 1 ratio, & there are many who think it's a good idea to find a 3.9 or 3.7 to 1 differential & slip that into the ute's axle housing when doing the conversion.
The only real downside to this is the increased unsprung mass which will degrade the ride quality of a road car a little.

If you feel you need even more strength [& weight] then the H190 differential will do the trick. This will NOT interchange into the smaller housings, so it would be necessary to narrow the whole rear end from the donor car.
There are other options of course, but these usually involve a fair bit of work & expense.

I have a 75 120y, Engine is a very high rever with good HP & Tourque.
I was told "by the so called Experts" the Ute Diff head would bolt straight in,

How does this go with the dif you have for sale. Apreciate your advise,

i have a 3.9 stanza h165 centre in melbourne pm me if your interested..

You use the Bluebird's DIFFERENTIAL. Thats the bit in the middle. To get it out, you remove the axle shafts, then unbolt it from the axle housing.
Remove the DIFFERENTIAL from your ute the same way, then reverse the procedure to install the replacement 'diff' in your ute. Don't forget to get a new gasket. When it's all back together, the whole thing becomes a rear axle assembly.
After all, you did ask about a 'diff' for your ute.
Remember that with taller tyres & a higher ratio diff, your speedo will now be reading slower than actual speed. Don't get needlessly busted.

with the diff out of a bluebird do you use just the centre or do you need to change everything?

Here we go again
Stock 1200 ute diff = H165 in 4.11 to 1 ratio
Series 1 & 2 Bluebird, All 5 speed & auto = H165 in 3.9 to 1 ratio
Series 1 & 2 Bluebird sedan, 4 speed manual = H165 in 3.7 to 1 ratio
Series 1 & 2 Bluebird wagon 4 speed manual = H190 diff [won't fit the ute]

Stanza, with Jap rear axle assembly = H165 in 3.9 to 1 ratio.
Datsun 1600, 180B, & early 200B wagons = H165 in 4.11 to 1 ratio

Wheel sizes? use a smaller tyre on the front & try to keep its O.D. down to somewhere near 560mm & you have no problem. Rears can be whatever you can fit. There is no real reason to run the same size tyre front & rear, just keep the size difference within reason.

its got a A14 but pulls way too many revs on the hi way. i tried 15 inch wheels but had too much trouble with the front

a12 or what? i've got a series 2 bluebird diff, supposed to be pretty strong and has a higher ratio, good for the freeway!

looking to fit a taller diff to my 1200 ute any hints would be appreciated