Summit Racing (18002303030) sells Wheel Vintiques brand in the sizes you are looking for. They stock the Magnum 500s but can order the Gt wheels.They also carry Cragar and American Racing(ttds are thee best looking in my opinion). THe 15x8 should work with a 4.5" BS. Guys correct me if I'm wrong.
1967 Mustang coupe:
16X8 VR45 w/ 245 nittos,
5.0L w/E-cam,1.7s & GT40 irons, MSD,Hooker super comps(jethot),Dr. Gas X, Hooker Aero Chambers,Meg's Tips, GT rear valence.
Master Power disc brake kit.
subframes, Auburn pro-posi and 3.25s