I think you will be fine with the 3.31. That 1st overdrive/5th gear keeps the six speed trannies from ******* it in 6th. I really dig how these things shift and lock the torque converter through 4th, 5th and 6th gears and not just in the top gear as old school trannies do. This is really noticeable when driving 25 - 35 MPH. Same goes for the 6th to 5th downshift at high speeds...no annoying converter unlocking/slipping.

FWIW, we have 20s with the 3.73 rear, which is probably overall gearing that is close to your combination.