The main points of beams have been hit on already but I’ll provide some feedback on the kingpin stuff. Kingpins got a bad reputation in the 1450 hay days because a lot of guys went to billet beams and just ran a simple bolt to locate/lock the kingpin from spinning. There is a problem with that design as it doesn’t shove the kingpin itself into a “corner” of the beam end. If you look at the factory wedge bolt that locks the kingpin in the beam, it’s a tapered wedge that forces the kingpin into the wall of the kingpin hole which drastically helps reduce any rocking or play from happening, so if you design a billet kingpin end make sure it still uses. Wedge of some sort.
I’d definitely try and keep the kingpin beams and spindles on this Truck. The kingpin beams offer great bump travel thanks to the “s” on the ends and ground clearance as well since they are such a short beam, and are a solid platform to start building off of. 65-79 Ford trucks have very flat front frame sections which doesnt favor bump travel so having the beam ends curled around the frame will help a ton, take a look at the Camburg Kids green F100 for some good ideas for lower ride height and lots of up travel. It seems every Uniball/Heim beam i have ever seen ends up being really tall which limits up travel, or they are shaped like hockey sticks. Plus you’ll loose turning radius due to misalignment spacers maxing out. Again, kingpins win here. You can design new spindles to add some additional KPI for larger tires, or run higher offset wheels to help as well but really taller tires alone help fix the scrub radius on beams.
But yeah, radius arms basically flat at ride height, beam pivots a bit higher than radius arm pivots, sitting with 50-55% shaft showing, it will be money.