Not much they can do there because they still have to use the factory UCA mounts, which dictate the size of the bolts.
The better question is, why the desire for fully adjustable UCA’s while retaining the small ball joints? Since that will likely mean retaining the factory brakes and small bolt pattern, which means probably not running really wide tires, which reduces the need for a fully adjustable UCA anyway.
But if you really wanted fully adjustable and wanted to keep the factory small ball joint spindles, it might be worth reaming those spindles to take a large upper ball joint so you could use the SPC’s.
