Twin I-beam front suspension or mono?

Your truck has the twin I-beam front suspension. The single I-beam is the strongest suspension system and is used on large trucks, but it is the worst for ride quality. The original versions used kingpins for the steering pivots. Those also were very strong. The twin I-beam suspension is a compromise. It's still strong, but today they use ball joints which aren't as strong as kingpins. The advantage is each front wheel moves independently of the other, so less road forces are transmitted into the passenger compartment.

The biggest disadvantage of the twin I-beam suspension is horrible tire wear, regardless of how precisely the alignment is set. "Camber" is one of the three main alignment angles. That is the inward or outward tilt of the wheel, as viewed from in front of the truck. The best system for tire wear is the "short / long arm" (SLA) suspension. Those use a long lower control arm that's parallel to the ground, and a shorter upper control arm that is angled downward from the pivots to the upper ball joint. That system offered superior ride quality and excellent tire wear, and reasonably good strength, but it went away in the late 1980s on cars due to its weight and complexity. It is still used on most light trucks except for Ford models.

Since newer twin I-beam systems use ball joints, the alignment, (camber, in particular), can be changed with offset ball joints to help tire wear, but doing so is a tedious, usually one-time affair. The problem with this system is camber changes wildly as the truck bounces up and down as you go down the road. A wheel standing perfectly straight up and down has 0.00 degrees camber. If you can imagine a wheel tipped out so far on top that it is laying flat on the ground, that would be 90.00 degrees. In practice, a typical camber spec would be roughly 0.50 degrees positive, (tipped out on top), plus or minus 0.50 degrees. The SLA system keeps the wheels within that range regardless of how high the vehicle bounces up and down. The solid I-beam keeps both wheels exactly in specs except when one tire goes up or down on the road separately from the other one. Tire wear from those motions is negligible.

The twin I-beam is the worst system for tire wear because it reacts in a major way to ride height changes. By far, the worst vehicles in the world for that, and the easiest to see it on are the Bronco 2 and Ranger 4wd. When they're raised on a hoist, both wheels drop down and they're tipped out on top a real lot. Where we can get good tire wear with the SLA system that keeps camber within about a 1.00 degree range, the twin I-beam system lets them go through a range of well over 20.00 degrees. The only time you'll get decent tire wear is when the truck is sitting at exactly the specified ride height. While it's in motion, the suspension is moving up and down, and camber is constantly traveling outside the specified perfect setting. Tire wear on the F-250 and 350 isn't as bad as on the Bronco 2 because they're wider. That means there's less camber change on those vehicles for a given amount of height travel.

Chassis ride height is critical on all vehicles when it comes to alignments and tire wear. You can visit any tire and alignment shop and look at their little books that show every year and model, what the height specs are, and where to take those measurements. The only systems not affected by ride height are the single I-beam, and the older trucks of other brands that used a solid front axle on 4wd models. For your truck, when the coil springs sag from age, the truck sits lower to the ground, and the wheels pivot inward on top. All conscientious alignment specialists will measure ride height first, and not perform the alignment unless they are allowed to correct it. That generally means installing new coil springs, or adjusting torsion bars on those models that use them.

Even though the SLA system provides the best tire wear, and is always adjustable in some way to put camber in specs, you will still get miserable tire wear if ride height has sagged. Tire wear with the system in general is superior because the different lengths of the upper and lower control arms make the wheels go through motions that reduce wear as the vehicle bounces up and down. Those control arms travel through very specifically designed-in arcs. When the springs have sagged, both control arms pivot upward putting them in new starting spots when the vehicle is standing still. They travel through the wrong arcs now as the vehicle bounces. In these instances, camber, and the other alignment angles, can be adjusted to compensate for the lower ride height, and that makes the numbers on the alignment computer screen look perfect, but those numbers only apply to a vehicle that's standing still. Bouncing up and down on the road is where the poor tire wear comes in. Lower ride height also makes the lower control arms on SLA systems no longer parallel to the ground. The result is the tires scrub sideways back and forth a little, adding to accelerated tire wear.

Replacing coil springs on SLA vehicles is a big and dangerous job, but I have a huge shortcut, as long as the vehicle is on a hoist. It can be done on the ground too with a floor jack, but crawling around underneath is not fun. Replacing coil springs on trucks like yours can be done rather easily with just a floor jack and jack stands.

This drawing below shows the left side of your front suspension system. My blue arrow is pointing to the pivot point for the left beam. There are no pivot points with the single I-beam system. The red arrow is pointing to the pivot for the right I beam.