The 15x7" with 4" backspacing should be ok in the front because you kept the small bolt pattern. 15x7, 4.25" backspace is what the big bolt pattern disks need, but they also widen the track width compared to the SBP KH disks.
Not sure what rear axle you have, but if it's a 7.25 with the SBP a 4.5" backspacing will likely be too much.
