Well...looks like the "6Shooter" is in a festive mood.
:L
As for the new "Dexos" standards for various lubricants used in current GM vehicles...to be honest, I know enough about Dexos to be dangerous and have yet to get the time to research it. Of late, I've been very busy on the next installment of the CAC's "Ruthless Pursuit of Power" series. The only recent engine not covered in that series of the LS7 and I'm doing that article now.
As for what oil would I put in my newer and older cars, I use Red Line 10W30 in everything except my 71 hot rod. In that car's big block I use Red Line 10W40. Red Line works very well in current roller tappet engines and old flat tappet engines as it's phosphate content is about 1100 PPM. Red Line is pricey, but I view it as...(and I'll use a cliche phrase you hear a lot in oil threads)...cheap insurance.
If I was on a tighter budget for oil, I'd use Mobil 1 10W30 where necessary. It is wasn't necessary, I'd use Valvoline 10W30 petro-based oil.
For engines with flat tappet cams, if cost was a key issue, I'd use either Chevron Delo 400LE 10W30 or Shell Rotella T 10W30.
At this point, I can't tell you what of those, other than M1, meets "Dexos".