I have decided to run 3.73 gears because will work really well for 30" tires I have, and will work OK for 31" tires if I go bigger in future. I won't ever want larger than 31" tires.
Edited in Later: 3.73 would be ideal for 30s, and OK for 31s, but 4.1 would be better for 31s.
(3.9 reverse cut gear unavailable for high pinion D30)
I like my 30 x 9.5 R15. So I'll have to wait and see if I really want 245/75R16 load C (31 x 9.5 R16), or just stay with 30s.
I won't change gears until I make a permanent decision on tire size.
For now, I'll just drive the 30s with 3.55 gears for 10K miles or more before I decide.
Warning: I often edit my posts a few times to get them complete or correct errors.