Been watching this thread for a bit, figured I'd comment on a few items here:
I would stay away from beam drop brackets. They transfer stress to the chassis and cause cracks.
If you need to reset the camber, you can move the lower ball joint out further on the beam.
The springs ending up closer to the tire is a good thing, your dampeners are right out close to were the force is being generated on them.
Drop brackets are fine if they are designed well... A well-designed drop (lift) bracket will be wider than a stock bracket to distribute the leverage over a wider part of the frame. This should avert issues of cracking (indeed, this was a very common occurrence on F-150s with kits that retained the footprint of the stock brackets). Another consideration is handling... drop bracket setups tend to handle a little better, with improved stability on steep and/or off-camber climbs (the higher pivots of modified beams increases the jacking rate of the suspension which can provoke instability under certain circumstances).
Where modified beams show their true benefits is at speed (and is why they're so popular on the go-fast scene). They have a lot more clearance, making it less likely you'll strike something during a launch/landing or hitting a dip in the road (an embedded rock sticking up, for example). However the center axle u-joint being at a constant angle can cause a vibration while driving in a straight line while in 4x4.
If speed-running is in your future, then the argument for modified beams is indeed very strong, however I would suggest sticking with drop brackets (keeping the axle geometry stock) if this is to be the more-typical expo type rig.
Don't know if this needs a quantitative measurement, but I'm a bit worried about the angle where the tie rod ends mount to the knuckle. The mounting surface on the knuckle in my mockup points downward at a pretty large angle. Perhaps this doesn't matter, or the drop pitman arm is also angled down to match so the planes swept by the pitman arm and knuckle mounting surfaces are both declined an equal amount below vertical. My "level" is based on the idea that the previous leaf springs would have mounted on a flat surface, so keep that surface level. Doing so angles the steering as described. So if you're out there that's all I'm wondering presently.
Hopefully I understand your concern correctly...
When it comes to the steering, what you want to aim for is having the steering linkage's movement be "in phase" with the suspension's (axle beam's) movement at static ride height. This provides the least amount of toe change (bump-steer) with changes in suspension movement/suspension loading ("In-phase" means the steering link (tierod) is aligned (parallel) with a straight line that runs between the beam pivot point to the knuckle where the tierod attaches, suspension at static ride height... In other words, the end of the tie rod will "point" directly to the beam pivot when at ride height).
To accomplish this, there are several different pitman arm drop heights available, along with the possibility of flipping the tie rods to the top of the steering knuckles.
I personally know of four different pitman arm heights that exist, each in 2" increments (from lowest to tallest):
- OEM 2WD Ranger/F-150/250/350 (this arm is almost completely flat, with no drop)
- OEM 4WD Ranger/Explorer
- Standard-issue aftermarket dropped arm (Skyjacker pt# FA400, Superlift #1109, etc.)
- Skyjacker "Extreme" drop arm (pt# FA600)
I'm not sure which OEM arm the E-series vans use, but I wouldn't be surprised if it's the same as the F-150 arm (they should all be interchangeable, being the same steering gear). If so, that would give you three increasing height levels for aligning your steering up with the TTB axle.
Also, you want the D50 axle beam pivots to be at the same height as your wheel hub centerline (this again at static ride height), which can affect the placement of your steering as well.
I wrote this article awhile back for Ranger/Explorer guys that were having steering issues after putting lifts on their rigs. The principles apply just the same to a F-150/F-250 setup, so maybe you & the OP can find some use out of it as well:
They still eat tires.
Camber changes as the suspension cycles.
So where do you set your alignment? Rig loaded, or empty?
'Cause it matters! Especially with a full size that may gain 1500 lbs when loaded for a trip.
Food, water, gear, people....
If the steering is set up correctly, suspension loading shouldn't have an appreciable impact on tire wear (as was said, a change in camber has FAR less impact on tire wear than, say, a change in toe alignment
, which is a much more common reason for a TTB to eat tires, especially one that's been lifted).
Of course this doesn't entirely invalidate the question of aligning the rig loaded vs. empty... I'd probably go with a medium load unless you know ahead of time what the vehicle's loaded weight will be and that it won't be varied a lot.
Another option might be to put air springs (bags) in the front coils to allow changing of the ride height.
There are lots of different ways to tackle stuff like this.
Anyway, hope that helps. Indeed it's great to see others putting TTB suspensions to good use. Solid axles do have their place, but no doubt ride quality isn't one of their hallmarks.