Ackerman steering is the concept behind the wider front track. Less oversteer, and better handling.The term "Slip angle" becomes far more important when considering larger tires of a 4wd.
Make a turn at speed with equal width axles, and the vehicle will try to lose traction to the rear tires (oversteer). This is compounded by a tire that is larger and has a greater amount of sidewall flex. Making the front axle wider helps to maintian additional control.
Weight capacities are also a contributing factor.
Contrary to popular belief, it is not so the rear tires can obtain a different line of traction that the front.
The small amount of difference puts the tires in roughly the same track. Most vehicles differ ony an inch or so on each side. Not enough to put the rear tires in anything fresh.

Notice heavier capacity vehicles have a greater width in the front than the rear. Compare a dana 60 front and a dana 44 front from the same era truck. Notice which one has a greater capacity and which of the two is wider.

This is different than a 2wd truck where drive tires and steer tires are a different dimension. These tend to push more than a 4wd.
4wd trucks typically require the same size tires in the front than the rear.
This makes Ackerman steering quite critical.


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So do people need to take "slip angle" and Aackerman steering geometry into consideration when choosing wheel off sets or tire size or have the Ford engineers already taken care of it and built the suspension that way?

Oh no, you leave it the way that it is. You do not want to change wheel offsets from front to rear on a 4wd truck, unless you intend to change the Ackerman angle.
Doing so will have a negative affect on Ackerman angle, and then you wont be able to rotate tires.
This angle is accounted for and engineered into your vehicle already.
Changes like wheelbase will also have an affect, as well as really tall tires that have soft sidewalls. This is where the slip angle comes into play.

Your front axle is wider for a good reason, though some feel that it looks odd.

Notice many off road race vehicle, and see how much this width difference is. Even in 2wd trucks. This is a fairly stable platform. Too much and the steering gets too fast, but keep it reasonable, and the truck can feel fairly swift while maintaing control.