Here's why I spec'd what I spec'd for me. Like Rick posted, maybe this will help whomever decides to go this route.
I purchased my truck in February 2017. I needed a truck and didn't have any reason to wait for a newer bodystyle.
Let me see if I can answer some of the questions re. my configuration and why these work for me. Remember, you can basically build these trucks to fit your specific need.
My truck has a 215" wheelbase. I wanted my truck as short as possible since my 5th wheel is 42 feet long and I wanted the 730 floor plan. I don't have a smart car and I don't plan on getting one. I am not concerned about resell, or what the next guy will do with my truck once I have passed on.
At 215" of wheelbase, the maximum amount of fuel that the software would allow me to carry was 200 gallons (100 on each side). That's what I have.
With the ET hitch, my overall length is 65'. That is the max allowed in my state. My 5th wheel does not have an option for a shorter pin box, so I'm right where I need to be.
The 2.93 gears were the tallest gear a single axle 730 could have at the 80,000# spec. This allows the truck to cruise at a low rpm at 70-75mph for the best fuel economy. On the 7%, 13 mile grades, the truck downshifts and powers up the hills without issue. I drive the speed limit.
Drum brakes. The disc brakes are substantially more expensive than the drum brakes. At least they were when I purchased mine. The rule of thumb is that the disc brakes cost more up front, but the drum brakes cost more to replace. Given that I tow a 22,000# 5th wheel and use the Jake brake (VEB), I will probably never have to replace the brakes on my truck. I have not had any issues with my brakes or stopping my unit.
My D13 has the eco torque 1550/1850 ft lbs. The way that it works is that in eco mode it uses 1550ft lbs and will uprate to 1850 in the top two gears if it needs the extra power. If I select the performance mode, the engine stays uprated at 1850 until I disengage the performance mode. Power has not been an issue.
I live and drive in cold climates in the U.S. The block heater, i'm told is overkill, but otherwise that explains the cold weather equipment.
I didn't get the TPMS. This is a good option, but I decided against it since I pre-flight my unit each time that I drive it and check and fill the tires for both the truck and trailer each time. Some may call it OCD, but I live by the words; Take care of your equipment and it will take care of you.
I don't believe that the LED headlights are standard. All of the lights on my truck are LED, including the headlights and BOC lights.
I have the locking rear axle.
I have the Hendrickson 13,200# air ride front suspension. A sway bar is not offered for the air ride. Only the steel spring ride.
I didn't get key locks on my DEF and Fuel tanks since I have the anti-siphon screens in all of my tanks.
I'm sure that I didn't answer all of the questions, but at least it gives you an idea of what you can do.
The key takeaway is that if you are going to go this route and build a new truck, do your homework and build the truck that works for you. After all, you're the one who's paying for it.
Stay safe Gentlemen.