Different ratio gears for a NV4500?

I read somewhere of different ratio gears available for the nv4500 currently you you have 4th at 1 to 1 and 3rd at 1.67 to 1 I'm looking for something in between so I can stay on the low side of he transfer case and get some higher wheel speed. From what I understand the low side is the stronger way to pull. Does anyone know of a mfg.?

the 6 speed (NV5600) has another gear in between 3rd and 4th im not sure of the ratio

They have a 1.39 in 4th but I want to stick with the 4500 better parts availabilty and the 5600's are not cheap. I will just need to get a couple of hooks on the truck to find out if what I have will work and then go from there.