If you don't care about milage and you want to keep on accelerating in 5th you would want the 600r with the .82 overdrive. The other one would be too big a jump from 4th and is more or less just for better mileage IMO. If you want different opinions on gear ratios you need to include tire size and what you plan on doing with the car, how fast you want it to go top speed, do you drag race and anything else that may help.
