As far as I know, and I’m not in the loop only the grindhouse for the Italian cut IB tech was released to donors.
And since I’m not a donor I’m not even sure an HD scan was shared.
There was a combo project on the web at some point in DVD quality using the scan with the laserdisc and the blu-ray to fill in gaps and replace the Italian screens with English ones.
Its quite unfortunate you have the choice to buy the Blu-Ray if you don’t already have it, i have the DVD. Or you can watch a DVD from the laserdisc if you can find one on some place like usenet or something.
But there is no quality release that isn’t some fanedit. And if you want something in retail HD quality you can forget about it.
If American Graffiti and THX 1138 were Star Wars we’ve already have a 4K 71 and a 4k73, a 4k77 THX and 4k78 Graffiti original director’s cuts.
Its not just the lack of interest its Disney Lucasfilm, and fear of their litigious nature. And the fact there is an official 4K for American Graffiti which is the 1998 cut redone with DVNR and a 5.1 mix. But has the redone credits and cgi sunset. And people don’t want to jump the gun because Warner’s is likely planning an official 4K for THX 1138 with George Lucas of the 2004 cut.