Ah, Kestas, sounds like you've got some real expertise here. The last year for the linerless Vega aluminum engine was 1977, but the last year for the Cosworth Vega was '76.

The GM etching process was flawed in that it was not always consistent. Some areas might be heavily etched, but others might have no etch at all or very little. Then the rings would tear off bits of aluminum an score the cylinders, and this was accelerated/exacerbated by overheating due to loss of coolant.

As is so typical of GM, they gave up about the time the process was perfected due to the bad publicity from the earlier models that had problems, but Porsche licensed the process from GM/Reyonlds for the 928 that went into production in '78. Mercedes and BMW followed suit. They all improved the etching process, which virtually eliminated the scoring problem and continue to improve it to this day, as the current generation of engines with integral aluminum bore wear surfaces or aluminum liners are developments of the original GM/Reynolds technology.
Interestingly GM has stayed away from it ever since, but the upcoming LS2 and LS7 engines in the next generation C6 Corvette have larger bores than the current generation LS1/LS6, and my hunch is that they may finally re-embrace the linerless technology that they pioneered.

If the cylinders don't score these aluminum/silicon blocks can last virtually forever as the wear rate is about one-fifth of cast iron. As I previously stated, there was no detectable bore wear on my Cosworth Vega at 70K miles and that includes about 4000-5000 miles of race track hot laps - the equivalent of the "48 Hours of LeMans.

Duke