Gear ratio and 38.5 inch tires

I'm looking to throw some 38.5 inch Boggers on my 1981 Suburban.  I'm sort of new to the off road world, got the bug, bought a rig, started a build and now my wife doesn't understand me.  Anyway, I'm looking for advice as to what gear ratio I should go to with these tires.  My rig runs a 454, bored out 30 over with the 700r4 transmission and a 6 inch lift.  The only time it will be driven on the street is traveling back and forth to the fire house, which is a 16 mile round trip on a back road.  I'm aware that I'll have to do some trimming here and there, which is all good.  The thing is, my suburban is a dually.  I bought it from a guy in Idaho who used it to pull his horse trailers.  Any advice from you veterans is greatly appreciated, thanks.  

I have a k5 blazer with 40's on it and i have 4.56 gears. I think if i had it to do again i think i would have went with 4.88 or 5.13's. The burbs are really cool rigs, but i think if you were going to make it into a wheeler i would swap out to single rear wheel. But ether way its really cool.  

I was wondering the same. I have a 2011 Tahoe with a 6" Lift and it has a 3.73 and was thinking if i needed to change the gear to a higher one.  The tires are a 325/65/18  

Check out this chart on gear ratios. its pretty helpful
http://www.4lo.com/calc/geartable.htm