I think some of, if not most run on E85, and other mixes that bring their 93 ron up to 100+.
I think your right gaz by saying if it blows it cannot handle the power, however in some cases if a built block blows, it doesn't necessarily indicate that the built block couldn't handle it. It could have been run on the wrong fuel or abused some how.
And your other point about the boost is also interesting, as they probably do run it lower, however it is also interesting to see them ran at the highest boost levels when the engines under the most stress, drag etc...
I think it is accepted that in stock form no Japanese engines can touch the strength of the 2JZGTE, however no even some Skyline tuners are venturing further and further with stock internals. R.I.P.S Are leading the way there and over time the UK tuners are following the same direction.
The same thing happened in the UK Subaru scene a while back, whereas previously stock STI blocks were not taken over 350ish, in recent times many take them up to 440ish without issues.
Jamie I also agree with you that our roads couldn't handle a power monster as big as that kind, and maybe that's why no-one has bothered.
However it still is interesting in the differences across the continents.
I think that maybe the Supra tuning field in the UK is extremely advanced especially with people like Whifbitz breaking barriers by entering competitive cars into TA, and building bigger and better cars each year. As said it would be nice to a see a UK car get their one day, but when I think will probably be a different matter...