one thing not considered.... a smaller diameter tire will give the effect of a different final drive. i run 245/45-17's these increase my final drive. i havent done the math now that i have the 3.29's but when i had the 3.73 gears for my DOHC, it made it equivalent to running a 4.10 ratio on stock tires. so im guessing my 3.29's with the same tire is more like a 3.69
another thing to consider is that the load on the engine will be different as well. since 60mph isnt really 60.
my advice is if you have access to a tuner to tune it. this way the speedo is right, and with a proper tune the shift points will be right for the load at the new mph and that you don't have KR due to a change in the final drive ratio.
