The only other gear ratio available for your current 3.90:1 setup is a 3.38:1 ratio. These gears have been back ordered for quite some time now, but I think the wait is over! I was able to aquire a set from Golden State Truck parts and they said they had just got them in when I called. It's quite pricey though, ~$400 for the gears and ~$200 for the complete install kit. Those were the prices for just one axle and I believe you would have to both axles on a 4x4 truck (Ouch). I think I would just learn to drive slower.
I know what you mean about driving at highway speeds though. I have 54 GMC with a 261, SM420 4-spd, and 3.90:1 rear gears and the engine really revs at 55MPH. That is why I am changing my rear gears this weekend. I want to be able to drive my rig to some out of state shows this summer and I would like to cruise at 65MPH. Good luck with your project.
Jim
