Back spacing and tire sizes

Those 70 series have huge sidewalls. And quite a bit a bulge. You could go 245/70/15 4.25” backspace 15x7. Or 15x7 with 4.5” backspace if off shelf. Then thin spacers as needed.
235/60/15 on the rear with 7” width rims.
225/60/15 on the from with 7” width rims.