Finally bought full assembly manual and checked my valve clearance at 270,000km.
-Camshaft lobes looked worn through case hardening across 60% of the lobe, worn less than .002in (estimated)
-Valve clearance measured .002in tighter than factory specs across all but one that measured .003in tighter than spec. (measurements were done at 0 degrees Celsius and size error likely caused by differential expansion of steel valves in an aluminum head)
-Spark plugs: factory spec is .040-.043in gap, looked more like .080in and measured at .075in. Replacing spark plugs indicated 0.5Lper100km (highway) less fuel consumption. New plugs will pay for themselves in one oil change (8,000km)
#3 spark plug showed slight oil coking but not fowled. No replacement valve tappets needed.
Love this car!