Piper,
The easiest method, if you can get it, is to find the block casting # and verify it. It should be tucked down behind the starter. You might also have some luck with the #'s stamped on the "boss" behind the distributor.
If you can get either of those #'s, you can generally determine what you have on the inliner's website, or some other's floating around out there.
While Cbaymac is generally correct, the early 235's, splash motors, had the same valve cover and look identical to the 216's. The later 235's had the "4-screws".
My latest truck 1952, 3100, has a 1948 235 out of a 2-ton grain truck. Visually, you can't tell a bit of difference between it, and the 216 I've got in my 46-1/2ton.
