Scamp vs. Valiant
In those days, the Valiant Duster Coupes outsold the sedans by a wide margin.
The Valiant Scamps and sedans were about neck and neck.
The Valiant Dusters had the most powerful available engines , which no doubt added to their sales success. The 340 and 360 V-8 s weren't available in the Valiant Scamp and Sedan (Though in theory, you could get the Hi-Po engines in the Police Packages.
My Valiant Scamp started out with a Slant Six...until I swapped it out for a 360 4 BBL.V-8.
That was then.
Today 4 door cars outsell coupes by a wide margin, which is why most 2 door coupes have been discontinued.