Gears

Uh, what rear end? What is available for a 9" is not necessarily available for an 8 3/4. What is available for an 8 3/4 is not necessarily available for a Dana 60.
I have two cars with that kind of power, one with 3.91s and a 28" tire, and one with 4.10s and a 31"tire. Neither are driven a lot on the freeway, but they can be. If you plan on freeway trips at highway speeds, I'd probably pick a 3.55, as a good compromise gear. (3.55 was a factory optional gear from Mopar, and stock on a 55 chevy with a glide. I drove 180,000 miles in a 55 chevy with a glide)