"superior automotive knowledge" you must be kidding! That post is from from 40+ years ago recollections. You are correct - there was a whole suite of ADR 27's (and other ADRs) around the same time. The numbers restriction is in there somewhere. Memories fade. I now recall that ADR27A was the one that gave us the "ball bearing solution" (blocking the recycling system that otherwise screwed up performance by running engines hotter / less precisely on mixture / cooking the oil of the day). We lived with that one for over 10 years on the track. Off the track I will not comment...
The first time I had heard of Bolwell was in 1964 / 1965. A "Holden 6" Bolwell (Mk V?) held the lap record at Wanneroo racetrack until 1979... just shows how far ahead it was at the time. I cannot recall if that was "official" or "merely" used the official timing setup. It was well over 2 seconds quicker than the phase three I was involved with in the early '70's - light years in racing terms.
If Bolwell didn't make a 2 + 2 Nagari then one of his customers modded one. It would have been easy enough. There is an British racing green 2 + 2 Nagari I spotted on the Nullarbor Plain (Nundroo Station) fueling up in 1987. The 1984 "stock 302" 2 seater Nagari I drove blew off the racing spec phase three "HO" in a straight line, outbraked and out cornered it by an equally silly margin. Wheels or Modern Motors also did a comparison review a few months later and reached the same conclusion - it was around 1 1/2 seconds quicker over a quarter mile alone! Considering you can "warm up" the 302 for racing, it would have been utterly embarrassing for Ford and Holden at Bathurst. Visions of a Falcodore halfway down Conrod straight when a "racing spec" Nagari comes down the mountain, passes it and disappears before the chase... Yep, it was that really much quicker. Great high speed handling dynamics too. I still kinda regret not buying one (I had only just bought a house when the Nagari came out, the begging bowl was beyond empty).
BTW, the Australian car industry received the same treatment from the 1930s to 1960s when the local manufacturers were officially replaced by the foreign owned Holden and Ford plants. Meanwhile Jack Brabham designed, built and drove a world championship winning formula one car.
Shades of the aviation black boxes - Menzies awarded the contract to Boeing, who had to ask the Oz inventor how to build it(!). The original was at a Melbourne museum in the '70's - probably still there as far as I know.
I reckon the Oz gov at the time could not believe a local could manufacture anything, and ensured it was true by shafting them. Adding "political donations" from some major foreign firms did not help the locals much either (sigh).