I believe that the page that 53John3100 quoted from has the answer to your question,
Victor.
http://clubs.hemmings.com/clubsites/chevytalk/GMhistory/1934motors.html
You thought your casting number was 831231 but I bet it is 837231 which decodes to a 1933-34 engine.

"Master Series DA, DB and P Series trucks have block casting # 837231 and cylinder
head casting # 837230. Standard series DC block casting # is 473741 and cylinder
head casting # 473740."

Two other points concerning the "K4706976" number that you said was on your paperwork.
First, the line in red in above referenced page says "There is no evidence yet
as to whether there was in fact a Master Commercial Series DB "K" prefix "Commercial" motor". My point being that on comfirmation of your inspection, you may indeed have one.

Second, the number 4,706,976 after the "K" on your paperwork fits with the production numbers that are shown on the webpage. Do you see how your number fits between the Nov 1934 Master number of 4,690,665 and the Last 1934 number 4,708,994?

I would also like to add a link to a photo of a 1935 207 (206.8) engine from one of Tom Brownell's books that I found online so you can compare your
engine.

http://books.google.com/books?id=WL...B4Q6AEwBDgK#v=onepage&q=&f=false

Again, pictures of your project would interest a number of people.

Last edited by randy luton; 02/05/2010 10:26 AM. Reason: added photo
"Nothing astonishes men so much as common sense and plain dealing." - Ralph Waldo Emerson