That is really going to depend on what bolt pattern you have. If its a 5 on 4 1/2", you can get 15 x 7 from 80s 5th Ave or from squad cars. 15 x 8 will be a lot harder, maybe some old Ramchargers.
Any other bolt pattern will present a problem if you want factory style wheels with dog dish caps. The choices with 8" wide wheels were usually mags. Gene