Oh, and a correction so that when this goes in the archives I don't confuse anyone...
It's not the counter / lay shaft that has the splines that drive the front chain sprocket, it's the main shaft. The parts fiche calls it "Shaft, transmission" and it is part 13128-1164. It seems to go for about $87 from Kawasaki, and entire transmissions (used pulls) seem to be going for from $90 to $150 on ebay.
That same part seems to be common from 1990 and up... It is not compatible as the 86,87,88 models.
Given the only thing I think I need is that shaft, I'll probably just buy new. Unless somebody here needs some other transmission parts and wants to split the cost of one of the ebay full tranny's with me.
Now here's another question. What about carefully welding a bead, and had fitting and filing that back to be a "repaired" spline? I would leave the oil seal in and fill the transmission with sacrificial oil (all the way to the top) to manage the heat... and plan on possibly replacing the oil seal when I am done. Does that transmission oil seal come out without splitting the cases?
I think I can do the weld and fitting, and if it goes terribly wrong I am just right back where I started, needing a new shaft. Is there other stuff in there that would suffer from the heat?