Since this is in the handling forum, it's worthy to add that modifying your exhaust is a worthwhile thing to do to get modern day 16:1 ratio.....especially if you are running a smaller diameter steering wheel such as the Tuff Wheel.
I have the Fast Ratio in a few E bodies and would never go back. I have 24:1 power and manual steering in a few others and they will eventually go into the scrap metal pile along with my space saver tires/rims, 450 wheels, frame tie down brackets, and bumper jacks/j-hooks.
Not sure why you think you have a 24:1 power steering box. 15.7:1 is the spec for power steering in the 67 thru 73 fsm, 65 and 66 don't say.
So if you have power steering you have to do nothing to get "modern day 16:1 ratio" it been 15.7:1 since at least 1967.
Not to mention that a 16:1 ratio manual box, with normal length arms, has been available since the early 60's. So I am really at a quandary wondering where you get the idea that a 16:1 ratio is modern, unless you were around when the model T was new.
