Hi, I have the 3.07 in the rear of my 86 Auto, I like this ratio for my use.  The 3.07 was the performance option ratio for the model. I left my rear as is & played with the engine a little as I like the torque I have which is 350 horsepower & 547 ft/lbs at the rear wheels. It idles as smooth at 800 without a stall converter & gives 32 mpg on a trip. Fry tires the good old fashioned way