Dart Swinger 340 Drum Brake Mystery

It is quite possible, Human error-unavailability of correct parts-etc.
Chrysler built 4 speed HEMI station wagons and four door cars (even though it officially was not possible to order such)

So in your case if the build sheet and fender tag both match and you don't see any obvious signs it was switched then you could leave the drums ( not the best brakes ) or find and install the correct parts if you are restoring the car
to the way it was supposed to be. :salut: