While most months are somewhat possible, it seems that October is relatively common. My 70 challenger RT is an October 69 car, my 73 Barracuda is a October 72 car. I've looked at a lot of tags and this seems to be prevalent. Someone told me that E bodies were built in certain time periods with some anomalies for ordered cars. The "experts" seem to hold this information close to the vest (along with a lot more).
70 Challenger RT 440-6 EFI, 73 Cuda 416-6 EFI
05 Hemi Durango, 01 Ram 4x4, 14 Ram 2500 4X4, 10 PCP Challenger 6 spd RT, 01 Viper GTS ACR, 52 B3B w/330 Desoto Hemi, 70 Hemi RR (under const)
9 x Challengers. AAR Cuda, 4 RR, 2 GTX, 4 Chargers, etc... (too many to list)