I wonder what the 2F/H55F combo would feel like at altitude in Colorado? I'm trying to keep mechanical mods to a minimum, but it feels like the stock gearing may need to be addressed as well.
Go get two FJ62 front diffs. The fronts are used a fraction of the rears and have 4.11's instead of 3.73s of the fj60
I imagine that would help a lot especially in conjunction with the H55F
Also depends on which Colorado altitude

We have a fair variance....4K to 14K