Rob,
Welcome. First, you probably posted in the wrong area for a Kirkham buyer, but Bob has been very helpful to all.
On the rear end, I was going to go with a 3.23 rear when I was thinking of going with a wide ratio toploader. I'm now thinking I will go with a TKO600 when the actually show up (I'm told monday). With the TKO600, I get an overdrive gear that reduces my cruise rpms. Like Tom K says, I don't think there is a bad rear end choice with that transmission. The 3.23 with a wide ratio will give you good cruise rpms and with a big FE, low end torque shouldn't be a problem. Traction will be the problem. Here is a gear calculator I like to use:
Gear Calculator
I believe Kirkhams come with Autometer gauges instead of Smiths.
The Kirkhams also provide a couple of tire choices. I went with the Yokohamas. They are at least T rated.
Good Luck on your choices.