SPC Performance 68-73 Ford Mustang Adj. Caster RodsModern radial tires require alignment specifications that differ from the original factory specs developed for bias ply tires. For caster, SPC recommends +3. 00 of caster to promote improved return to center and more responsive performance. Stock strut rods on the 1st generation Mustangs and FoMoCo vehicles are non adjustable and often have worn out bushings that can cause excessive movement of the lower rod assembly, resulting in poor handling. A