2w0s060

The car is currently running 4.56's running a Nitto 315/35/17 on a stock WS6 wheel. I am looking to purchase a set of four Weld Pro Stars 15" wheels. The problem is while I am crossing the line we are hitting rev limiter or shifting into 5th. A 4.10 gear would actually be ideal. What I would like to know is what rear tire size will lower the car to approx. a 4.10? I will be running the MT ET Radials. Also what back spacing is going to be needed?

Thanks