Try this style T/C kit, http://www.thezstore.com/page/TZS/PROD/PSDC10/23-4190
I have seen them on ebay pretty regularly also.
They fit on the front of the rod, urethane or rubber on the rear after the TC box mount. They are solid so wont compress under heavy load or cornering, but they still allow the rod end to pivot as the suspension moves up or down. I ran mine for many years and only switched to fully adjustable type during my rebuild.
With the shorter springs, if your having trouble with too much droop or non captive springs, try a shorter shock like Z31 300zx. The 240z KYB GR2 gas will be great with the king springs (I ran this exact combo), with a 23mm front bar and 18mm rear, it'll handle like a go kart!