The 240 and possibly 260 shafts wont fit. The rear flange is too small and the 4 mounting holes are too small also.

48 minutes ago, ennisdavis said:

The 240 and possibly 260 shafts wont fit. The rear flange is too small and the 4 mounting holes are too small also.

No offense, but this is completely incorrect.  The outer shape of the flange changed over the years, there are square and round, but the bolt pattern and size is the same for all of them.

It does look like the automatic got a different bolt at some point though.  No year is specified.  But they do interchange.  The same size bolt through the same size hole, through all of the years of the Z. 

http://www.carpartsmanual.com/datsun/Z-1969-1978/power-train/propeller-shaft/2

Just finished the auto to manual conversion on my 78. Drive shaft completely interchangeable. Changed diff R180 to R200 no difference in bolt patterns. Like @Zed Head mentioned flanges may be round or rectangular bolt pattern does not change. However,the ZX turbo T5 trans has a larger diameter yoke but the pinion flange remained the same. 

I forgot the one that I usually remember - 1975 has a different pattern and maybe bolts.  It is unique among the Zs.

On 9/30/2021 at 4:29 AM, Zed Head said:

They will.  But the first year and a half, about, of 240Z's used a shorter shaft.

Because of the diff re-location to the back. Didnt even think about this, I knew about the diff but the driveshaft offcourse has to be longer to. 5+

The 2+2 driveshafts are also longer right