Trace,
I could not find an illustration for the 350EW, but I found this one for the 600EW which has a similar cable release mechanism.

My basket-case ’27 EW 350 is missing the exhaust valve lifting mechanism, but it does have the sleeve that threads into the top of the crankcase. This sleeve is identical to one fitted to my ’28 600EW (also missing the exhaust valve lifting mechanism!), so it is probably just the length of the operating rod that varies between the large and small engines. The square loop on the end hooks onto the exhaust valve lifting link; the end of which is very similar to the clutch operating cam.
If your crankcase has a bolt blocking off the hole in the crankcase, it is likely that the operating rod is also missing. The same might be true for the pair of forged links that bear on the exhaust tappets, and so lift the valves.
-Doug