This. Couple things. The temp delta test is designed to monitor under set parameters: Unloaded, constant throttle, at 55-66 mph on the highway. When you add the trailer and towing load you start to change the parameters. Now the engine is working harder and warming the oil more because the oil is doing its job. Plus if you dont know the oil age, or type there could be a couple factors there. If it were mine I'd change the oil with some good Rotella T5 or T6 or Valvoline Blue. and I'd change the coolant. At that mileage I would NOT chem flush it. And dont belive the internet bS about 10,000 distilled water flushes either. Drain the shit, pull the block plug on the drivers side and the radiator petcock and refill with a decent Diesel ELC additive coolant. Then I'd re-do the temp delta test. I bet youll be happy. It doesnt have "factory head studs" because those are mutually exclusive. It either had factory head bolts or has been converted to head studs. Again..there is ZERO chance I'd ARP stud a head at 300k mils if there isnt an issue. Honestly I wouldnt if there was an issue. AT 300k you are too close to in frame service interval. If I went that far into a 300k mile engine it'd be a long block VT365. If you decide to delete EGR absolutely replace the oil cooler at the same time. Otherwise Id change the fluids, which are maintenance items anyway, before I tore into it. Scott does great work and has deleted two 6.0s for me. 1 word of caution. Pay the extra $100 for the "good" EGR bypass if you go that route. He put the "cheaper but just as good" one on my 07 and fought it for a while. He stood behind it and made it right but he had to tear into it 3 times to get it to seal. If it were mine...Itd get an oil change and a coolant drain and fill. And Id give it hell.