A truck, like a pick-up? What are you using it for as far as hauling? Any towing? How much?
A GMT800 2500 8 lug LQ4/4L80e/14 bolt rear discs brakes is a pretty darn bulletproof drivetrain; that's what just about everyone here uses for landscaping, construction, etc. GMT900 has similar engine and rear end, but has the 6L90e which is more problematic and expensive to repair.
The equivalent 1500s are still decent, but will have the lighter duty transmissions and rear end. If you don't need high payload or towing, they are good options and get better gas mileage. On the newer 1500 trucks you do have to deal with AFM/DOD stuff, but not on the HDs. All of this also applies to the SUVs.
If you are in the rustbelt, things change because a lot of these older trucks I just mentioned have been long gone due to rust, so you may be looking at newer trucks simply by what's out there in your region. Or go south and purchase a southern truck, IDK.
Good luck.