that is a great ratio combo. I am looking at a np 5 speed transmission. the ratios are almost identicle. the difference is that 1st gear in the 5 speed is much lower at 5.6. the .73 over drive is ideal and will work very well with a 3.55 to 4.11 rear end. with 4.11 gears the overdrive works to give you an effective rear ratio of 3.00. Put simply another way... if you were tacking 4000 rpms at 55 mph you would now be tacking under 3000. the last numbers were made up for comparrison.
