The supposed quote was really a paraphrase originally by Charles Binderup 19 March 1937 in the House of Representatives (Congressional Record—House 81:2528):
It was Henry Ford who said in substance this: 'It is perhaps well enough that the people of the nation do not know or understand our banking and monetary system, for if they did I believe there would be a revolution before tomorrow morning'.
The above was also published in the 19 April 1938 Social Justice on page 10 where it is attributed to "Representative Charles G. Binderup of Nebraska"
The 1957 opinion article by Russell Maguire "How Internationalists Gain Power" in the American Mercury volume 85 pages 79-80 states:
It was Henry Ford, Sr., who said in substance, "It is perhaps well enough that the people of the nation do not understand our banking and monetary system, for if they did, I believe there would be a revolution before tomorrow morning."
Later sources may make this sound like an exact quote, but "in substance" makes clear it is not an exact quote.
What Henry Ford definitely did write in his 1922 book My Like and Work at page 179 is:
The people are naturally conservative. They are more conservative than the financiers. Those who believe that the people are so easily led that they would permit the printing presses to run off money like milk tickets do not understand them. It is the innate conservation of the people that has kept our money good in spite of the fantastic tricks which financiers play-and which they cover up with high technical terms.
The people are on the side of sound money. They are so unalterably on the side of sound money that it is a serious question how they would regard the system under which they live, if they once knew what the initiate can do with it.
In summary, it seems that a paraphrasing of Henry Ford has been mistakenly identified as an exact quote.