Advice on changing from stock 14 inch rims and spacing

On older cars, 'backspacing' is the term that's used.
On modern cars/wheels, peeple tend to the use the 'offset' term, which is measured differently.

On factory Mopar-wheels, the backspacing is usually about half (+a little extra) of the total wheel width.
So a 6" wide wheel will usually have a 3.25"-ish backspacing.

Anytime the backspacing is less than half the wheel/rim width, the entire wheel sits further out to the fender.
Usually on A-body Mopars, this is not what you want (especially on the front wheels).