The S10100 Drag Race spring is recommended for all applications where you are using a larger aftermarket cam, including road racing. Max recommended lift on the Drag Spring is .600" and max recommended RPM is 9500.
The S10149 Spring is for use with very high lift cams and in applications where high spring pressure is necessary. Also recommended for 1000hp+ turbo SFWD Applications.
S2018 Beehive - Endurance / Medium Duty
S10149 - Drag Racing - High RPM Large Lift Cam
S10100 - Drag Race/Road Race