I'm trying to figure out what I have here.
The part in question is an NOS front amber side marker assembly, part number 3579405 on the box.
That number in the parts book checks to 71 Valiant rear ??, and 71 Dart as shown in book.
I have never seen an amber rear on a car.
Second picture shows an actual 70-71 Dart amber front lens alongside this assembly I have....they are obviously different.
So what exactly does this NOS assembly fit
Is a 71 Valiant all by itself?
Thanks in advance

The NOS unit and 70 Dart lens below...

It is not uncommon to have mistakes/typos in parts books. I would say the Rr/rear is one.

The part# in the book is 3479405 but you said 3579405 is on the box. Is that a typo on your part?

When you say "The NOS unit and 70 Dart lens below" do you mean the pic is below or in the pic the nos lens is above with the 70 dart lens below it? I am asking because my 70 dart has the top lens (with the chrome). I don't think the bottom one is for a 70 dart. I am fairly sure the 70-71 Darts all use the top one.

Sorry for the confusion, the part number on box is 3479405, same number that is in the parts book.
The top lens and housing are the NOS.
They definately do not fit in the 70 dart fender opening.
The lens on the bottom was taken from a 70 dart, I just removed the lens from the housing.
Notice the bottom lens has a flatter nose which is characteristic of the fronts in a 70 dart fender.
The top unit will fit in the rear quarter no problem, but if you take a look at your 70 dart you will see the opening to the fender is not the same rectangle shape as the opening in the quarter which has more of a pointed edge.
To complicate matters more both lenses say 70L but both are obviously very different, bottom lens wont come close to fitting in top housing.

Top one with housing looks like Challenger

Nope, definately not Challenger,.....I own one.

I think this dilema may have been solved after a conversation with someone I consider to have expertise in this field.
This person was once informed there were no Hemi 4 door cars, even though he does currently own one.
When running these lenses some where injected amber as well as red for rear for use on export vehicles.
Makes sense as this amber lens is in the same housing as the red rear uses, same cast number 3403689.
All amber front assemblies have the attached pigtail wire with female/male end, be it Dart, Challenger, etc.
This doesn't, but rather has the provision for plug in wire like all rears have, thus it is an amber rear.

That makes sense, In the past when I shipped Corvettes & muscle cars abroad some countries I would have to put reverse light lenses in with amber bulbs on the brake/park light side