Ok, first off, a wilwood pro spindle is taller than a regular everyday Mustang 2 spindle, so by putting one or the other on, changes the instant center, therefore changing bump steer characteristics, you can't just use a taller spindle, so if a suspension is designed based off a regular everyday Mustang 2 spindle, that's the ONLY style spindle, that should be used, if it's designed for a wilwood pro, that's all that should be used, dropped or not, that makes no difference, it's the upper and lower ball joint distance between the pivot points that matter, and you can't simply shorten or lengthen that distance, and not change the geometry.