I need to post some pics of the thrust bearing I took out of a motor knocking on 200K... It was damn near untouched...

Don't sweat it, cut your filters at every oil change to keep an eve on things and keep beating the hell out of it... Your tune is more important than changing the oil

 

As long as you have a good (conservative) tune and run good gas, the engine will be the least of your worries. I've personally seen at least a dozen of these things, both 5.3s and 6.0s, with over 300k miles and still pulling good oil pressure (in the construction field, none the less). The old adage "they don't build them like they used to", used in the positive sense, isn't exactly correct. If the engines "back in the day" had the power today's engines do and turning similar rpm, they wouldn't last near as long. It's amazing how tight the tolerances can be on a mass-produced engine now-a-days. The materials have gotten much more advanced as well.

The transmission will give you the most trouble since it's basically a collection of free-wheeling parts controlled by braking action (clutches). Next will be the front differential (4wds) and then the rear axle, in that order usually.

 

^^What he said.

 

Run it till it blows. My DD work truck( its and oilfield truck. lease roads suck) has close to 200k at the moment nothing has been rebuilt. My work truck is 3/4 ecsb 4x4 with the 6.0. It has a CIA and a Bully Dog GT.

 

As far as the short-block goes, mileage alone isn’t really the determining factor. As long as it was maintained and is in good shape, it could last a very long time. Where things progress a little faster is in the cylinder heads and especially the lifters themselves. Lifters by far have the tightest clearances of any component in a modern V-8 engine and they will exhibit wear faster as a result. In the heads, valve-guides, seals, seats, valve-stem’s and of course the springs themselves will start showing wear. Of course seals and gaskets will deteriorate from heat and use and need replacement sooner than some other components. I would perform a leak-down check on the engine and send out a sample of the engine oil for analysis. If everything looks good, it will give you a basis to make a good judgment call on for future modifications or if you really do need to go ahead and start considering purchasing or building another engine now. Also if the bottom end comes back passing mustard, which I bet it will, if you do find you are experiencing a little more lifter tick than normal or the tail-tell signs of valve seal or guide wear, at some point I would try and set aside the funds for freshening up the top end and replace the lifters while you have the heads off.

Beings your about to perform a cam swap, I personally would at least try to determine the condition of your valve-guides while your swapping the valve-springs by manipulating the valve-stems side to side to get a feel for how much play may be starting to develop.

Of course it never hurts to have a spare bullet on hand, especially if you have the extra coin to do so. You could take your time and build it, all the while continuing to enjoy your truck and if something did happen down the road, you wouldn’t feel so pressured to come up with something and of course if you’re like me, things never happen at the best time in the world. Ultimately, a good state of tune will enhance the likelihood of keeping your current engine alive, even at 10 to 12lbs, however if you like to push things to the ragged edge in the tune-up and beat on it, bad things can and will eventually happen.

 

Well said.