backspacing

so im thinking myself to death trying to get this figured out. i have 14x7 wheels with 4"bs and the tire i am running sits a little close to the fender side. i just upgraded to new dr diff axles with the large bolt pattern and am trying to find a set of steel wheels to use with 255/60 drag radials. in a perfect world i would use a 15x7 with 4.25-4.5 bs but the only wheels i can find like that are the police wheels.

that said, the only wheels i can find with those dimensions that are similar to the mopar wheel s have a +12mm offset, would that effect where the wheel and tire are located? or would i be ok with them?