After starting my coilover coversion and strut shortening I've found that the insert retaining cap for the Stanza struts doesn't go over the top of the R31 Skyline inserts I'm using. The inserts come with two different threaded caps but neither of them fit either as they're too big for the strut tubes.
The two options are to machine out the inside of the strut nut to accomodate the larger insert or to get the strut tube slightly enlarged and re-threaded to take the strut nuts that came with the inserts.
I'm going with option A to start with as strut nuts are slightly more replaceable than struts!