I have some Ward's Yearbooks that give some numbers by percentages, but I don't think they started tabulating 4-speed numbers till 1961 or '62 - I'd have to check.
On a related note, here's something interesting from <span style="font-style: italic">Automotive News</span>. Haven't perused the earlier years to see if there's a similar tabulation.
http://i.imgur.com/lfYqShd.jpg?1