That's looks messed up badbud! You sure you didn't get the live axel H&R spring instead?
Anyway, this is how the Steeda ball joints should
work. Mounted in the end of the a-arm the taller ball-joint raises the spindle in relation to the ball joint pivot point. This has the effect of moving the wheels UP in relation to the body and control arms (thus lowering the car to the ground). The benefit of this compared to springs is that you wouldn't be changing the control arm angle to achieve this drop.
How is this beneficial? Take a look at the drawing:
The green lines are finding the instant center of each suspension side, the point where both green lines meet is the instant center. For a McPherson strut the suspension instant center lines are 1) The line parallel to the control arm and 2) the line perpendicular to the kingpin line at the upper mount.
Once we have the instant centers of both sides we can draw a line from the instant center to the center of the tire contact patch that is furthest away. Where the two lines meet is the car's roll center. This is the point that the body will roll around
as weight transfers from one side to the other. You want the height of your roll center to be as high as possible to keep the amount of body roll down. Although other considerations will limit you from getting the roll center really high; too much downward pitch will likely never be a problem for a Mustang. More often the Mustang suffers from too much upward
pitch in the control arms (and IMHO I would consider anything over parallel to be too much).
As you can see in the drawing, figures one and two have a nice downward inclination of the a-arms, these drawing arenâ€™t to scale or indicative of the Mustang but they can still illustrate the point. The roll center heights for both figures (which are where the two red lines intersect) are almost identical in relation to the body of the vehicle. But as you can see the upward offset of the wheels has resulted in a lowering of the body to the ground (which means a lower center of gravity (COG) - good).
In figure three we have lowering springs that are pulling the a-arms in an upward inclination to lower the body; this is actually much like how my GTâ€™s a-arms currently rest. The COG is lowered a good deal, which is nice, but the roll center is almost sitting on the ground. That means when this car goes around a corner it will have a much more obvious pitch to its body roll, and that will more than likely result in some nasty camber loss - which is detrimental to traction.
So should the Steeda joints work? Yes, as far as I can tell, although I would worry about their strength in the new geometry (theyâ€™re putting a lot more stress on the new joint <that's a guess>). You still would want a heavy spring rate to combat some of the nastier aspects of Mustang body roll, but these could help things along.
BTW: Let me know if you think I messed something up or left something out. The above is the best that I can do at my current level of understanding (without hitting too much detail). I am welcome to some critical review.