In 1970, Challenger R/T's had to be big block cars. In 1971, you could indeed get a 340 R/T. My problem here is it states that this car was originally a 340-6-pak car. Was that option available in 1971? 
That is setting of my "BS" detector. 
Mike
...the only "factory installed" 340 SIX PAKS were in the '70 T/A and AAR...part of the A53 package
...Mr. Norm, Grand Spaulding, did build some 340 SIX PAK cars, but they weren't factory
