The 85 and 87 have different part #'s for the output shaft, buuuuuut......They could be dimensionally the same. The difference could be as simple as a difference in heat-treating method.
Well, I compared my 87 and 94 shafts. They don't match! Oh, wait. You knew that already.
Besides the sprocket retention method, there are some differences, but I will tell you what is the same first:
Shaft splines.
Shaft length from step at sprocket end to the clutch end.
Shaft diameter at all bearing and non splined gear contact points.
Gear thickness at shaft.
Now for the differences..... The spacing between the snap ring grooves. That is all for the shaft. (except for what you already knew!)
It seems that Kawi made an update. On the 87, the gears that were retained to the shaft with snap rings had plain snap rings with tabbed thrust washers. On the 94, they did away with the tabbed washers, and went with tabbed snap rings. Getting rid of the washers subtracted .040", and since the gears are still the same width, they moved the grooves on the shaft closer together to make up the difference. The same is true with washers (minus the tabs) for the clutch side of the gear closest to the sprocket, and both sides of the kick idler gear.
Some pics: (87 on top, 94 on bottom)
In this pic, second gear in from top right is the tabbed washer. Center gear at bottom has the tabbed snap ring sitting on it:
Closer view of snap ring groove spacing:
Imo, I would do the 89-04 shaft, but make sure you get
all of the snap rings that go on that shaft. If I was doing this, I would be completely comfortable with it.
BTW, you owe me a six-pack now!
torch