I don't think I would be as happy running anyone else's stuff. BMR is of the highest quality and their customer support is extraordinary. Kelly is their Mustang guy and I've spent many a phone conversation talking about set ups and what is going to work best for my application. I wouldn't go with anyone else. There are other great companies out there making great parts, but I've had nothing but success with them.
And if you call Kelly he can explain why it would be better to go with the later model UCA over the one made for our cars.
Thanks for the kind words about Kelly and BMR. I'm glad to hear how much you enjoy our parts. Just a heads up, I'm the new sheriff in town and Kelly is handling all of our S550 stuff, while I've taken over S197. So if anyone has any S197 questions, feel free to contact me directly.
OP, I think that an adjustable upper and fixed lowers are the way to go. It's much easier to adjust one arm instead of two, and if you don't adjust the lowers properly, you can throw off your wheel base and thrust angle. For example, if you go too short or too long on both arms trying to hit your desired pinion angle, the wheel base will be off. If you adjust one side more than the other, you may throw your thrust angle off and have issues with the car not wanting to track straight.
While the mount isn't required, it's not a bad idea. The OEM arm has teeth built into the sleeve to allow it to bite into the factory mount. This prevents the arm from moving around in the mount. The factory arm just deflects, it doesn't rotate like an aftermarket arm. Our sleeves are smooth, so the smaller OEM bolt and lack of teeth allows the arm to move around in the mount.
The 11-14 arms are also a better design than the 05-10. They come with larger, stronger hardware, and the arm is longer. The longer arm results in less axle movement during suspension travel because the arc is less dramatic. The mount was also changed to compensate for the longer arm. Upgrading to the 11-14 spec arm is really easy and requires no extra work, just an extra $4 bolt from Ford. I did this on my 08 with our monster bearing upper control arm.
If you have any questions, feel free to call or email me!