Is your plan to build it and trail it, or to use it as a DD and get an 80 or similar as a trail rig? I think that's the question you have to decide. Low mileage is appealing if you are going to use it for both. But if you're looking primarily for a trail rig, then $31k for a truck with 165k is probably a winner... swap your mods over, sell your old truck on car-part, and pocket the difference in $ for repairs or future upgrades.
Honestly if it looks clean I'd go with the $31k/165k option as it's no longer $10k difference for 100k miles... now it's $20k, and that buys a lot of future repairs (like it will cover an engine *and* transmission rebuild down the line. Even better IIRC your A/T was recently rebuilt so swap that over and sell the wrecked LC with the older transmission)