Monster power can do that, but a stiff suspension combined with years of fatigue and or rust, can cause the paint to crack in that area. It is a factory body seam that can crack. Although it is often just paint or sub-filler crack. It is very common, and usually not a huge deal. It's not a fatal sign by any means. Look closely for rust elsewhere. C-Clip? I only know of a handful of C-clips on a Z car. Shifter, throttle linkage, brake linkage, clutch linkage maybe, and a few other places, if that is what you are asking. Again, RUST, RUST, RUST, and it can be hidden very well, so look deep. A little bit of rust, the size of a dime, on the lower portions of the car, is often the tip of a large iceberg.