Exactly.
The only setup that would work is 15x8 all around. 225/45/15 up front, and 205/50/15 in the back. With that combo the diameter is within .1" and is the only combo that would work.
Obviously then you can't rotate tires and depending on your alignment they will wear out quick. You will have to most likely up-size to a huge front bar and balance the rear accordingly. All this work and then it begs the question, why didn't you just get a good track car to begin with?