One guy just messaged me and asked if I thought it was a real hemi RR. Or not. I told him I figured it was a factory screw up, for sure. Yea, I know it was a real hemi RR.
I would also bet real 340 Dusters came factory with dual exhaust.
Years ago I built a 318 Duster out of a slant car, before it was popular. I built it for me. Got the car from a friend in town that bought it new. I should have just keep; it original. I was bored. I also welded in the bracket for the dual exhaust, just for me, no one was trying to fool people back, then, the "clone: was not even invented quite yet. Heck back them few people even lusted for a real 340 A body. Too many big block whatever cars around, even the 67-9 BB A body was not that hard to find...cheap enough.