I developed these over the past few months not so much to solve a problem as to enable more usage cases. Instead of trying to adapt S14 parts with hit or miss lengths, here's something bespoke for the Z31 that encompasses a huge range of adjustment options with less pieces.
They will work on all years, they can be extended way over the stock part length, and are much stronger. There's a long blurb on the site: http://responsetype.com/shop/fairlady-z ... e-rod-kit/