So I just got this 1956 3800 pickup and I have a lot of questions. I'll start with just a few.
What size is the engine? I was reading through some posts about size and numbers on parts but I'm still not sure. On the head is a casting number B60 848. On the block lower edge by the distributor, stamped numbers 033125IF5bXB. I guess the lower case "b" could be a "6".
Then a part number for the oil filter and what weight rating for the engine oil was recommended for this engine.
More than likely a 235. If you look just above the starter, are there 2 vertical bars stamped into the block? If so, it is more than likely a 261. Also, there should be an engine ID stamped into the block by the fuel pump. Take a few pictures of that side of the engine and post them, you'll get some better assistance.
-Patrick 1953 Chevrolet 3100 261 / 4-speed / 4:11 / Commercial Red
We can better help you ID your engine, with those codes.
The second number I posted is on the ledge by the distributor. 033125IF5b XB This is a stamped in number, not cast. Located the same place as the green painted engine in the link you posted. I will look for more numbers.