My Crown V-8 has 15" rally wheels on it right now with 215/65/R15 tires. I'm still trying to lower (numerically) the ratio since 1st gear is useless and 4th gear is running 20 mph per 1000 RPM with the stock 3.55 gears. I thought of replacing the gears with 3.08 but cannot find anyone who knows how to do it plus it is costly. Doing calculations, if I upgrade the back tires to 235/70R15, my effective ratio would be 3.20:1 which would help. I'm not sure if they will fit. I have tool that simulates tire/wheel size but thought I would check with my fellow V-8ers first.
Larry
Simsbury, CT