Hi Myke,
Sorry to hear about this trouble. I do not know what brand piston is in there. I know who put the big bore kit in "Mad Jack", he liked Wiseco back then, but there is no guarantee that is what he used, the original owner would have chosen what brand, sometime in the 90's I suspect.
If I were you, I would hone the cylinders and install new pistons and rings. It is not horribly expensive, and you would have piece of mind for many more miles. APE has a good selection of quality stuff for the KZ.
kzzone.com/
The engine were it still in my hands would have been rebuilt eventually, It was the weakest link, although solid enough for the time being. I am surprised a stuck ring did not damage the cylinder wall. The thought I had about the engine was a real big block with mild compression pistons. Avoid going too big or you will over heat the motor. Valve guides should be replaced and the crank inspected for alignment. For about 2K you could have a real punisher of a motor, complemented by the ignition module I installed and the flatslides. You will not be disappointed.
If the tensioner is broken, make sure you find all of it. I broke a cam chain in another bike once, when some debris from a broken part did not get removed, the bike ran along after fixing initial problem for years, then one day it just got caught up in the cam chain and whack ! broken cam chain totally stranded.
kzzone.com/blocks.html
I will shoot you a text so you have my number, but it is still the same as before, even though I am now in Washington.
Ted