Before getting too crazy with transmission swaps, etc, you might want to read our
Techtip on swapping out your rear axle's third member for one with a 4.10 ratio Heck of a lot simpler than what's been discussed so far....
And the 4.10 is a heck of a nice improvement over the original ratio. I've done it in my AD 1-ton and was quite pleased. One of our users (mrf1002u) was honchoing a swap deal with the rock crawlers -- they wanted our original 5.x ratio third members and were swapping us their 4.10's AND covering the shipping. All we had to pay for were the new gaskets and oil to refill the axle.
Just my uninformed personal opinion, but I think your truck would be pretty gutless with the 3.x gearing.
