I put my H55F into this 60 of mine at 300,000 miles. I'm currently at 348,000 miles. I would say that with a light truck (stock wheels and 33" tires, front bumper, no winch and a stock style steel bumper in the rear) that the 3.70 gears were perfect.
I've only added more weight and further stressed it. I've seen the mileage drop and it get a little slower. But also, this 2F has seen better days. It feels as if 4.10 would be perfect in my current combination.
I will still drive this anywhere fully loaded, but just keep my speed down to 70 max. There are times on the highway that it feels better in 4th gear than 5th, and I think thats telling me that its undergeared. I can get 12mpg in varying terrain and it will do 75-80 with my foot half way down. If I keep it at 65mph, I've seen 15+mpg consistently (adjusted for my gearing)
A proper 2F, 750 lbs of armor, H55F, 3:1 gears in the split case and 4.11 with at least a rear selectable locker would be the perfect balance of on/off road for me in a long wheelbase truck.
In our 3FE 62 with an H55F I'm leaving the 4.11 gears with 28" tires. It may stand a chance at staying in 5th gear over hills like that.