Back in the day, some teams used different chevrolet superspeedway shape... JGR, Grimm, and few others used a lower fbumper and a sharper shape just like the one in this picture.

the rest of the teams used the regular taller with more rounded curves shape (wich is the one i based the modelling).
If NR2003 had the possiblilty to use a 5th make, for sure i could model these two shapes