what does fit a Magnum?

[MikeW]

I've always been more of a 60'-70's classic muscle car era guy before this Magnum. Tons of wheel choices for them. Can anybody tell me why a lot of wheels don't fit Magnums? There are many listings for 17-18" x 7-8 wide with correct pattern and offsets, but most will state "do not fit Magnum". I find that it really limits my style choices, and I do have a particular look in mind for mine, but it's not with 20's or 22's. I would really appreciate being clued in on this?
Thanks