Who makes rims in our backspacing?

Depends on the car, what bolt pattern, how or if you have changed the track width (i.e. 73-up front spindles, B-Body rear end, or aftermarket axles, etc), Spring relocations, tubs, cut, rolled or modified fenders are just some of the things that can effect the offset. Oh, and wheel width and tire size.

For me. I ordered custom offset wheels from American racing to fit all my brake, body and suspension mods. Since it looks like you have a Duster/Demon/Dart Sport, 94-up wheels that fit a Mustang are typically a good start for fitment. There is a giant thread on wheel fitment to give you an idea.