I'm pulling my VC in about a week. If I found that in my 1998 I would be mortified. I agree, some seem to have "low" standards. The BITOG crowd is fragmented - there's the OCD crowd running nothing but diester oils in their sling-lube lawnmowers. Then there's the folks who are OK with buildup as long as the engine runs and wear a badge of how many miles and how little maintenance they do. Then there's everyone else in between.
I'm wondering if being a chronic old-lady short tripper wasn't a big part of it. I notice the inside of the VC looks about like the surfaces of the head. This indicates to me condensation etc... being a major factor.
Perhaps you should check or simply change the PCV just in case it's gunked up. If you like to run science experiments and put on enough miles to try all kinds of things for the board, I would mechanically clean the inside of the VC and all of the gasket surfaces with solvent. I'd be nervous to use a fast flush particularly on something I didn't know the history of. If the engine is working fine this isn't a "nothing to lose" scenario. At the same time I might not want to wait for ARX to do its thing since varnish isn't a forte of ARX.
I would personally be looking in the direction of LC20 or Rislone, I guess. Pull the VC to see how it's coming. After things look better and you have the majority of the visible crud cleaned, you could follow up with a single round of ARX for the rings and any other hidden crud you don't know about (if it's a keeper).
If it were mine, I'd stick with a good dino throughout, perhaps one known for cleaning, an HM variety, or an HDEO depending on your climate and use of the car. If you're using it for short-tripping, go on the thinner side.
