Interesting thing... The rx7 tail shaft seems to have new uni's and is the right length... Only rtouble is the diff flange bolt holes are spaced correctly on one parallel but not the other.

How troublesome would it be if I drilled the diff flange holes out until they are big enough that the furthest out edge of these holes lines up with the furthest out edge of the tail shaft holes evenly. Thus the bolts would not be snug all the way around but would still be on one opposing side to each other.

So instead of a 8mm bolt in a 8mm hole I'd have a 8mm bolt to one side of a 10mm hole.

Cant see any other way of moving the holes out precisely...

Or I could just suck it up and get another tail shaft made.

could you drill 4 new holes in your diff flange of the
correct spacing offset from the originals?
Also make sure the centre locator is the right size, don't
just rely on the bolts to locate it

Don't think I'd get the holes exactly correct. Can lath up a bush for locating ring as its a few mm smaller.

Had a good look at it last night and as much as it sucks to have to spend money on this project I'm going to have to get another tail shaft made. The diff flange is too small to modify.

you wont need a whole new tailshaft, if its the right length you can just replace the rear flange to suit your diff properly

or another cheapskate way would be to swap the diff flange with one from a stanza or other vehicle with h165 which might
allow you to then drill/modify it to suit

I've got the diff flange that fits the tail shaft but the nut on the Datsun diff flange is bigger than the one on the rx7 which suggest that it won't fit the pinion.

Do they make uni's with two different size pivots? The utes are considerably smaller so not sure how that would work.

I would think they need to cut off the rx7 diff end uni then adapt the Datsun one on, balance and fit new uni's.

yeah that's the go, just have the rx7 shaft modified to fit if its long enough. only problem i can see is
that if your datsun tailshaft is the original one then chances are the uni's are non replaceable

no big deal, your tailshaft guy will have a solution

pretty sure there are two and possibly more different size tailshaft unis. for one i believe the 120y/1200 auto tailshaft has bigger unis than the manual ones. And the diff bolt up flange thing is also different from the H145 (coupe) and H165 (ute) diffs.
In saying that some unis are different sizes as well as they are differently pressed on, some have a sir clip and other are star crimped...

Any suggestions where I can get an accelerator cable modified?

Have a look around but I know a speedo shop near me that calibrates speedos and fixes them etc also mods the cables and convert to electronic speeds etc. any speedo calibration shop should be able to...