^^^And that's why I'm not recommending post 2006 GM trucks to anybody.
I don't follow GM motors, but I know that like bendix driven stop/start , cylinder deactivation is garbage tech.
Interesting article here:
https://www.enginelabs.com/engine-tech/gm-escalates-cylinder-deactivation-with-dynamic-fuel-management/
Be really interesting to see what power trains Toyota installs in the new Tundra. If there is no cylinder deactivation among them you'll know why.
Many GM guys, myself included, will argue that the final pre-2006 5.3L and the 6.0L were the best truck engines - and likely the best truck engines we're going to get. Final LS series small blocks before government regs pushed GM to add cylinder deactivation, VVT, etc to get fuel economy and emissions in line. Unless you do something absolutely stupid, you're not going to kill one of those motors.
That said, the pre-2006 trucks themselves are not bulletproof...transfer cases, transmissions, rust out, front hubs, blend doors, etc are things that are all kinda suspect on the 15+ year old trucks. You've gotta remember, these are now pretty old trucks, by most standards, most have high miles, and have seen plenty of Canadian weather. These are also all relatively easy and low cost repairs....Even a trans R&R on one of these is <$2K.
If I was shopping for a truck though, I'd be looking for a 6.0L pre-2006 with the cleanest body/underside I could find...which probably means bringing something into Ontario from the West or South....And that'll cost as much as a much newer truck, but it's still what I'd do.