Let me give a bit of background so you know where I am coming from, I have run my own business repairing and modifying and restoring classic BMW’s for 40 years, now retired, I restore and rebuild vintage and veteran Matchless motorcycles and have modified a few vehicles in my time, not great on theory or calculations though!
Many years ago I built a camper that would carry a couple of motorcycles, it was based on a diesel Bedford CF1 bus, I fitted LDV front discs and callipers, that had the effect of widening the track, then I fitted a PAS rack from a BMW, it was a lot too narrow for the vehicle so I lengthened the side rods, it drove so badly I came straight back into the workshop and worked out the error of my ways, it suffered from bump tracking deviation, I removed the shocks and got some staff members to bounce it up and down, the tracking varied from toe in to toe out by say an inch when bouncing up and down! that would in turn produce bump steer depending on what wheel had better grip at any point in the cycle,
Basic Akcermann angle is set by drawing a line from the centre of the king pin to the middle of the rear axle, the steering track rod end centre should be on that line, so further in if the steering gear is behind the axle and further out if in front, that will make the inner wheel turn a sharper angle when steering so avoiding tyre scrub on cornering,
Try to visualise a steering rack much longer than yours with very short side rods, as the suspension compresses the short side rod goes to a much steeper angle so effectively shortening relative to the wishbones altering the toe angle a lot, and the opposite when going over a hump back bridge, factory suspension / steering stays relatively straight, we could set the basic tracking with a vehicle up on a lift and the suspension hanging and it was very close to spec when dropped to the ground, if you try that with yours you will find it changes a lot,
For basic setting we used an 8 foot light tube placed in contact with the tyre and eyed it up with the rear tyre (assuming the same track front and rear)
The Bedford CF1 was fitted with a BMW 635CSi engine and box… bit quicker than the 2.2 diesel!
Please don’t take this as a personal criticism I am just trying to pass on hard won knowledge! and solve the issue for myself!