Proper iridium spark plug gap

I bought plugs, AC Delco #41-985, and was planning to gap them to the recommended .060" for my 2001 Yukon XL 5.3. I have seen several sites on the internet that recommend not changing the gap on these AC Delco iridium plugs from .040". Do I gap these plugs to .060" or .040"?

Set them at the GM recommended setting for your truck