Shoot, that's not traffic, that's highway driving. Traffic is when it takes me 1.5 hours to get to work in the morning. And I only have 18 miles to go! Now THAT'S traffic! As far as gears go, I have 4.56s, a 700, 35s, and a 305 with 240,000+ miles on it. I have no problem going well over 80 MPH. And my truck is 8' tall from the ground to the top of the lights! Big wall to be pushing into the wind. Now, I also don't go that fast unless there is serious erason to do so.
When I had 3.73s and the same configuration, I ran only in D, wouldn't run in OD. I could still go 75+ without trouble on the highway. I was just running much higher RPMs.
So, basically, you'll be fine with either 4.56s or 4.88s. You just have to make the call as to how low you wanna go. But 4.56s will get the job done just fine and salvage some gas mileage in the process!
Brian
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Who put a stop payment on my reality check?!?