Are 1999 GMC Sierras good trucks?

I am looking into purchasing the 5.3L V8. Is the motor good and how long does it last. It now has 120,000 miles on it but runs strong.

they are good trucks but that is some miles to be on it, still although it can be a real good truck those engines held up really good,you have to replace the timing chains and gears in them although every 100 k,and id say that one is due one now,other than that it should make you a real good truck,they really did not don’t have recognized issues with them to make them bad trucks, so if you found a nice one and can get it at a great price id purchase it,,it should last you a while,if you take care of that engine it should last up to 300 k on that one,i have seen some go past that and their still going,with good maintenance you may be able to keep it on the road for a while,good luck with it.

been a certified mechanic for 37 yrs.

The 5.3 is a decent motor.BUT 120k is really pushing the upper end of it is life expectancy.

Is it a 4x4? If be sure to check the move and universals.

They are great motors that can run past 250K easily. there's only one catch. How well it was taken care of up till now. Is this a private sale? Can the owner show maintenance records of oil changes, transmission and differential services?
Care of the complete drivetrain is important.