I have nearly 80000 kms on my 4.3 and so far my only complaint was towing a 4000 lbs camper with some stuff in the back of the truck. The issue was not being able to keep it in 6th gear so I had to run at 105 km/h @ 2800 rpm in 5th. Would like to know how the 5.3 would fare with that extra HP. Other than its been good.