When replacing rear springs on a 1989 420 SEL, it seems advisable to also replace the rubber pads(shims), which come in 9.5mm 14mm and 19mm sizes. How does one determine which size to order? I'd like to have all of the parts before starting the job. Should one just order the 14mm and hope they are right, or go for the 19mm?

__________________
1989 420 SEL