Unless you're looking at an overdrive transmission, it won't make a difference. Most transmissions are direct drive in top gear.
Your rear axle ratio is 4.57 which is pretty low. Later axles are likely a higher ratio (eg.4.10, or even higher) which would help keep your highway cruising engine RPM down. Unless you're pulling stumps, you don't need a 4.57 rear axle ratio, although you could find an overdrive transmission, which would allow you to use a higher numerical ratio axle and still cruise down the highway at comfortable engine RPM's.
Thanks for the info Klhansen that answered my question!
