TT91 designed or had someone design a bracket for him using CAD. PM him to see if you can get that CAD file, then take it to your nearest machine shop. Chances are they can make you two of them pretty cheap with a CNC.
Oh yeah, you have to cut one of the brake bolt ears off the spindle, then drill a new hole, so be prepared for that. Mustang spindles are a dime a dozen, so you shouldn't have problems finding a new one if need be.