NCBowtie - if you are going to change out BOTH, the best streetable combo for perf and mileage is normally a 2004R (or 700R4) with 3.73 rear. There's a reason the factory likes this combo also. What kind of truck - C or K /10 or 20? Depending on what you have now, you might very well be able to only change ONE parameter (trans or rear gears) and get the desired end result. An O/D trans, especially a 2004R (with the lowest rpm producing o/d ratio - but also my favorite trans) may not be the best choice if you're going to live between 45 and 60 mph cruising. RPM may get too low in 4th. What trans and rear end combo do you have now? Are you certain 29" tires are the final solution? (Taller might be a good idea). Let us know what you have now and might have some good suggestions.
Here's a 3.73 and 4.10 comparison with a 29" tire. Very similar to javelin's chartm (clearly a fellow Excel geek
) - produces same #'s. But the one for you to focus on is the rpm @ 65 mph. And 1st gear overall ratio. 700R4 has a steep 1st compared to 2004R, so you'd be shifting out of 1st quite quickly, and it will chirp your tires quite easily with 3.73, probably TOO easily with 4.10s. Anyway. Something to stew on.