Are all S30 control arms and strut assembly interchangeable?  I've decided to redo my rear strut assembly.  I just wasn't happy with the final result.    

I see some for sale that only say they're for 260Z and 280Z, but don't say 240Z?

No, the struts changed mid-260Z.  Early 260Z struts are the same as 240Z and late 260Z struts are the same as 280Z.

What do you mean by "redo"?  I like to use carpartsmanual to see if part numbers changed.  Looks like the control arms, AKA transverse links, changed in august 1973.  Not clear what the change was though.

The axles changed in the cast hubs, somewhere in 73 for the 74 model year, but it looks there were a bunch more changes along the way.  Part #1 and 2.

http://www.carpartsmanual.com/datsun/Z-1969-1978/axle/rear-suspension

@Zed Head I rebuilt the entire left side suspension, but really don’t like the way control arm fit into the assembly.  My guess is that the bushings won’t last long.  I can go with what I have, but thought I may try buying used on eBay, hence my question.

@Jeff G 78 thx I’ll look at that more closely.

1 hour ago, wadelester said:

@Zed Head I rebuilt the entire left side suspension, but really don’t like the way control arm fit into the assembly.  My guess is that the bushings won’t last long.  I can go with what I have, but thought I may try buying used on eBay, hence my question.

If you didn't bend anything you could always go back to stock bushings.  They seem to be available.  If you mean the casting when you say "assembly".  You''ll be back to where you started but with new rubber.

http://www.carpartsmanual.com/datsun/Z-1969-1978/axle/rear-suspension/57

https://www.nissanpartsdeal.com/parts/nissan-bushing-link~55541-e4100.html

I read on the internet that the later control arms got beefier. Thicker steel and maybe some additional gussets here and there for strength.

I don't know if the form-fit-function changed when they got beefier, but if not, even though they are different, they may still be "interchangeable".

Here's some of the stuff I read on the internet. Some threads from HybridZ:

https://forums.hybridz.org/topic/51104-differences-between-the-240z-and-280z-rear-control-arms/

https://forums.hybridz.org/topic/64548-stock-control-arm-length/

Thanks to all...I'll ponder it for awhile.  I may consider going back to rubber bushings too.