This isn't quite accurate. The 16:1 ratio of the Flaming river box is faster than the "regular" stock 24:1 manual box ratio, but there were also 16:1 "fast ratio" manual boxes available from the factory as an option on some of the earlier cars. Also, ALL of the factory power steering box's have a 16:1 ratio.
As far as the number of turns lock to lock:
16:1 = 3.5 turns
20:1 = 4.5 turns
24:1 = 5.5 turns
Mopar Performance used to make a replacement worm gear with a 20:1 ratio, which is why I listed that as well. They're not currently being reproduced, but there are still some out there that pop up from time to time.
