Well oval chassis have most of their weight on the left side of the chassis to help it turn left better.
Sedans are made to have the weight spread out evenly across the chassis so it transitions better through left and right turns.
The Losi Bodies fit the electric sedans, and the bodies by protoform sit the oval chassis.
To set up a car, you need a motor, batteries( 4 cell of oval, 6 cell for sedans), a body(sometimes), Tires(sometimes), radio, servo, reciever, ESC, tire glue, charger, and power supply(sometimes. Also you need tools, and could use lubes, motor spray, a car stand, fans...etc