You can build it out of the box but the body lacks some lines in it, the chassis is the old MPC NASCAR chassis with torsion bars and leaf springs, although the new kits have upgraded suspension. The seat is also out of the old MPC kit and it was wrong. So I modified the body to get it right, re-engineered the chassis is to make it accurate, added a correct seat and modified the cage (it was lacking some bars). So, do you need to do all that to make a nice model? No. Scale Auto Magazine had an article on a box stock build and it was exceptionally well done. Very neat when done. I just wanted to see what it would take to make it better reflect the real car. Not necessary, but that's just me.