I am replacing my mono-leaf springs on my 1968 Camaro with multi leaf springs. I have the new springs with the new fronts bushings and the installation kit (OER), which includes the rear shackles and bushings, top and bottom pads, u-bolts and the T- bolts. plus the shock entensions. Is there anything esle required?? I have read that a shim is necessary to make room for the bolt that goes throught the center of the leaf springs when it mates to the rear axle perch, as the mono leaf spring perch doe not hae accomodation for the bolt??