Front wheels spaced far out

Factory discs and a 7 1/4 rear will give you what you see.

My 74 was the same way until I dropped an 8 3/4 rear in it from a B body.

The front tires stuck out quite a bit, with factory wheels.

That's a good point, the 7 1/4 rear is almost an inch narrower than even the A-body 8 3/4. The difference is even more pronounced on a Duster/Demon/Dart Sport, since there's a lot more room to the quarter with the Duster bodystyle.

But you can still fix it by adjusting the backspacing.