Sidehill: You can take that 5.14:1 stump puller and replace it with a '67-'72 4.11:1 out of a 3/4 ton automatic and it's a two hour bolt in job that will cut your rpms down by 25%, which in your case is a HUGE improvement.
I did to my '51 3/4 ton (which had the same rear) and it will really make things a lot easier on your truck, and you.
Here's a link to the swap:
1951 3/4 and 1 ton two hour rear end swap I think you'll find this a lot less surgery and effort than putting in an auxillary transmission or overdrive setup.
