Mike, De Sotos are all beginning "S" 1941 begins S8S and S8C.
With a 3 7/16" bore the stroke was 4 1/2" to get 250 Cu.in.
For those that might want to know:
Plymouth block serials start with (funnily enough) a P, Dodge with a D, De Soto with an S, Chrysler with a C, and U.S. Military trucks, with a T.
I Don't know about the Canadian ones.
If the number includes a star, I think that indicates U.S. manufacture.
On the smaller blocks, the cars had lighter cranks= less counterweights.
These cranks had 4 or 6 bolts to hold the flywheel on. They are also likely to be shorter stroke. The U.S. military Dodges, T 215 / 214 / 223 all had 8 bolts,and were a 4 5/8" stroke, which were better suited to revving hard.
None of this however, helps Kevin.
