Regearing is definitely an option. However, It would be more cost effective to just go with a turbo motor. I have one lined uf for $500 but I'm thinking about using it in something with a longer wheelbase.
Trail Tough's 4.16:1 tcase gearset is the smallest high range change available, and it is too low to keep the 31s with this engine. Going to 33s would split the difference and give me about 6% reduction from where I am now but it would also increase rolling mass and resistance. So, even though I would gain top end speed, I would not, likely gain any fuel economy.
I believe that I can live with 235s for a while, while I build another, longer, ride to mount 33s on. A Samurai on proper 235s is still quite capable.