I am not positive but I don't thing the screw is correct, I believe the spring is held merely by 2 tabs which sandwich the bottom coil of the spring. I just installed my on my 73 Cuda and I had to bend a tab up to remove the spring and bend it back after installing it. I am very sure mine didn't have any screw, of course that doesn't mean it was/is right either. I will look at my 70 Challenger and see what it has.
70 Challenger RT 440-6, 73 Cuda (under const)
05 Durango, 99 Dakota, 01 Ram 4x4, 14 2500 4X4, 10 PCP Challenger RT, 01 Viper GTS ACR, 52 B3B w/330 Desoto Hemi, 70 Hemi RR, 61 Jeep FC170
9 x Challengers. AAR Cuda, 4 RR, 2 GTX, 4 Chargers, etc... (too many to list)