Ells, I don't believe there were any significant changes between 90-91 models. Here's spec from archive. Dimensions are identical for the two years. You're probably safe to use the 90 clip.
I was just looking over a used parts house inventory and front fenders, grill, bumper cover and radiator supports were all shown common 90-91 http://www.3wave.com/arp/SUB.HTM#287
Couldn't find much more on the older cars.