As far as I can remember , the "A" bodies got a different driver's-side exhaust manifold for the 1971 model year ( B&E bodies' manifold stayed the same for 1971 ) .
In 1972 , a preheat tube and shield were added to the driver's-side manifold , as evapourative emissions' standards were changed ; this is a 50 state deal ( with 1 exception *... more on that in a bit *... ) .
So , 1968-1970 , all 340 exhaust manifolds were the same ;
1971 Demon / Duster got a log-style manifold on the driver's-side ;
1972-1973 had the same log-style manifold , but with the addition of the preheat tube & shield .
* = the 1972 Road Runner / Charger Rallye still had the "Ramcharger" / "Air Grabber" hoods available . These fresh air intake setups still had the tub-style air cleaner base / lid , and were devoid of the preheat tube .
The fresh air inductions -- so-named above -- were not supposed to be available in California ; however , I've seen no less than two '72 Road Runners that were original Ca models ( one with a 340 , the other with the base 400 ) , and had the "N96" hoods .
These were built in late 1971 ( the 340 car had a build date of 9-'71 , and the 400-powered R.R. had a build date of 11-'71 ).
I hope that this info was-is of some help :mrgreen:
