15" Steel Rims on a '68 Dart

I recently came across a set of red circle poverty caps for a good price and wanted to use them on steel rims on my '68 Dart. The problem is the fit. For one, it's a Dart so there's not a ton of room. I'd like a narrow 15" Mopar steel rim (6" wide?) on the front and I'd like a 15x7 or 15x8 on the back with as wide of a tire that will comfortably fit with minimal modifications. The second problem is my small bolt pattern. I came across a guy that has about 30 steel mopar rims I can go through. Any thoughts on what I should be looking for? I don't really know much about available sizes, back spacings, etc. for old mopar steel rims. Sometimes I think it would be easier to just call someone like Wheel Vintiques and order the right bolt pattern, size, width, and backspacing I need and skip the old junk. Any suggestions would be appreciated.
Thanks.
K.C.