They may need to be custom ordered. You may be able to use spacers to get to where you need to be, but you should measure first to make sure. I try to keep my plain wheel spacers at a 1/4" or less thick.
Just because a wheel is offered in a particular off the shelf backspacing doesn't mean that's what your car needs. Most of the other Mopar body styles can use a 0 offset wheel like that (15x8 with a 4.5" backspace is 0 offset). But an A-body 8.25" is narrower than an A-body 8 3/4, so with an 8.25" you need less backspace than what will work for most other Mopars, even other A-bodies with 8 3/4 rear ends.
