I'm heading up to the Talamena Byway new year week with our trailer.
Most popular things are the DIY intake setup, a free flowing exhaust (I just used a free flowing muffler), gauges to monitor all your temps and data, and then a chip with tunes on it tailored to your needs/desires.
The intake is sometimes called a Tymar intake, or a 6637. The filter was origianlly a Donaldson filter, and then people just used their own brand they like. I use a Baldwin PA2818 clamped to a piece of 4" exhaust, clamped to the intake tube.
Exhaust is your choice. Bigger allows less back pressure and lets the motor breathe more, which is always good.
Gauges can be analog or digital. I have the analog gauges, but I would rather go back and do digital. That way you can plug into the computer, read all the on board sensors, and then add your own you want to monitor. Most popular are transmission temp for auto trans, exhaust gas temps in the manifold to keep from melting the pistons, and boost for fun mostly. Monitoring things like boost, high pressure oil pressure (ICP), fuel pressure, and the like let you see if something might be going bad.
For your truck, if it's an auto trans, I would get a modified valve body to firm up shifts and reduce heat. Brian's Truck Shop in Lead Hill, AK is popular. John Woods also makes great transmissions and parts too.
For me, I also added an external spin on filter to help keeping it clean.
The best thing is to keep it cool. A trans cooler from a 6.0L Powerstroke is a direct bolt in
cooler that is HUGE compared to yours. Only thing to modify is the way the lines hook up. Easy.
After all that, people will get a TS 6pos chip and get custom tunes burnt onto it from Tony Wildman, PowerHungryPerformance, and many others. The custom tuners let you tell them how you want it and what you'll be doing. They can tune it to be safe for hauling a big trailer. They can tune it to change transmission paramaters to your liking. They can do anything you want.
After that, you'll never stop messing with it
Just a warning.
Also, if you don't understand how these motors work, read this: How HEUI works and best to convert
Where on the coast do you like to go?