I've learned a lot from this thread and another one in a different forum: Syncro II Left Shifter Problem

There are two versions of the Syncro II, pre-92 and post-92. I've attached photos of both versions and a diagram of the left shifter.

The pre-92 is as pictured in the diagram parken posted above. It doesn't have the same parts in the same configuration as mine. It has a more centered cable run on the left side. The levers have straight blades.

The later version, which I have, has a cable run on the left that is right on the inside edge of the shifter body, and distinctly, has a cable adjuster on the right side. The levers are curved.

I think 8 speed might be the point they changed (mine are 8)

The above linked thread goes through that and also this web page has a lot of information. The last gasps of Syncro ~ tears for gears

Thanks for all the help. I'm hoping this thread can help future people who are setting up these beautiful shifters. I'm pretty sure my problem is that I have the little concave washers installed incorrectly, and I think I need to add a spacer (i.e. flat washer) between the frame and the shifter brass bushing to push everything outward so that the screw can tighten down better. I think the boss on the frame is a little too long.