[aerohead]

Aerodynamic drag dominates the road load power at these racing velocities.Rolling resistance is essentially meaningless.
The weight will impact power-to-weight,so it's important to acceleration.
The weight will also impact traction,as many of these cars are capable of wheel spin at over 250 mph+.
Some racers add ballast to improve grip.
Spins are potentially fatal.If the car goes sideways and lifts off,if it lands sideways it can dig in and barrel roll.The centrifugal forces and accelerations of the crash can easily exceed human tolerances.Only an onboard fire is worse.