The difference IS the 6bbl on an E-body!!

Quote:

For 1970

CHALLENGER
N95 - Evaporative Control System - required on all cars registered in the State of California N.A. otherwise .......... $37.85
N97 - Noise Reduction Package - required on all cars registered in the state of California equipped with 440-6 engines or 426 Hemi .......... N.C.

This info is taken trom the 1970 Dodge Pocket Salesman's Guide posted on Hamtramck Historical.

N97 - Noise reduction was accieved in different ways on different body platforms, again California "only".
E-body - eliminate N42 "bright exhaust tips" from 440-6 & Hemi cars.




I will "assume" Plymouth's 'Cuda was dealt with in the same manner (in California).