I also second the notion that a fully 35mm sourced version of it is one of the last “holy grails” of the OT for me. The Belcubus and Puggo/Jaxxon presentations are nice, but both have their limitations (being sourced from TV airings and 16mm optical, respectively).
I do wonder if the original recordings of those sources could be dug up. If I’m following the chain correctly, the mono audio on these restoration projects is all processed to some degree - it sounds very much to me the “35mm Mono Mix” that’s on both 4K77 and Despecialized has audio artifacting, and it also sounds like a faint reverb effect was applied to attempt masking those artifacts. The software used at the time that track was created (am I right that those specific finished Mono tracks are now about 10 years old?) would be pretty out of date now, and 10 years is a very, very long time in terms of what audio programs can do so far as cleaning and restoring audio.
re-capturing the VHS mono audio (or even the 16mm audio) might be worthwhile too, if that’s possible. I’m coming very late to this, and I’m not trying to cast aspersions on the work that was done all that time ago. But I do think if it’s possible to re-capture that audio source, it might be worth trying, to see if that mono audio could be given a slightly better once-over.