1973 Plymouth Duster 340 - 4 Speed w/ Posi

I'd almost believe that if it was a plain jane car.
Being a 340 4-speed car I doubt that's the case.
Somewhere there is a slant six car that no longer exists, and this once rough 340 car is now an original "rust free" or "95% rust free" western car.

Ad stated car was a sure-grip rear diff vehicle.
Were all 340 4-speeds?
How else would he know... Unless it had a fender tag/build sheet at one time.

I'm not saying the O.P. did it, but it's pretty obvious someone used this Duster 340 4-speed for a rebody.