I didn't read everything after the OP. But I have always made my own repairs till I had to rely on other choices as I got to old to do everything myself with my injuries from a 42' head first fall some 33 years ago. But stay on top of all my repairs with my mechanic, and not a large shop. My mechanic works out of his own shop on the property he lives on.
One thing I would do, is make sure the main electronics are working and computing correctly. Then most of what you said is good to go if you would buy a brand new short block. you still need the majority of the parts you already invested in to assure a brand new complete engine. This is if your 2016 truck is in as good a condition as my 2006 Z71 with the same miles on it, or close at 168,000 on mine.
Mine is paid for, I would just buy a complete long block since I've done none of the top end replacements you have, and at 10K dollars I would have a reliable power plant, meaning the only other big ticket item is the tranny! This is as long as you have maintained it as I have, all difs transfer case, and fluids changed at 100,00 miles besides the oil and filters once a year, I use the premium amzoil in mine. so my last three have went over 250 before I sold them with originol motor and using no more than one quart in the 12k miles average between oil changes, never adding as I change it before it down a quart.
But if yours has been taken care of my suggestion would be choosing a 10K inverstment for another 8 years of use. Most likely trouble free. Or do as I did 2 years ago and price a new truck, stripped down, over 42,000 dollars. My Z71 has every option and loooooadddded, with HD payload and trailering package. so for me to get the same thing I have now, I would be looking at over 70K dollars. you decide, I hope your option is the same as mine, and if you take normal maintenance as serious as I do,,,,,, you make the call, I'm happy with this,,,
Not new but I would drop 10K to keep driving it over spending 70K to have newer with little more to offer. But this has the L33 5.3 engine, and why I bought it when I did with low miles. That engine uses no VV timing, no fuel management, and has a higher torque cam, LS corvette cathedral port heads and 10:1 compression, witj h all aluminum block new at the time the only 5.3 with floating wrist pins and upgraded forged rods, with thicker cylinder walls than any other 5.3 block. It was also only ever available in the 4wd extended cab PU both Chevy and GMC, and no other model for only 2 years. This was why I bought it. NO, this is not a hot rod, but will run for over 300K miles trouble free and not use oil, with more power to haul than the other small blocks at the time, and still give better gas mileage, it averages over 17.3 mpg every 10 to 12K miles between oil changes and will give me over 20 mpg highway kept under 65 mph on trips. Even though it is not a race car, it will quite nicely get out of its own way!!
If you know what you got, and after 180K miles were happy with it, and think it was the truck you wanted, put a new heart in it and enjoy! I would with mine! Even if you had to buy a new tranny later, now everything is reliable again and only a fraction of what that new option is, you'll pay what the trany and engine costs for the next 5 years to break even, by then you'll be back where you are now with the new one? like was said, only can decide!
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