If there are 21 studs the block was built 1932 to 1938. The transition to 24 studs was late in 1938. Check the water petcocks on the front of the block next to where the lower hose from the radiator enters either an inlet fitting (1936 and earlier) or the water pump (1937 and later). It the petcocks point straight down it is a 1932 block. If the block is not a 1932 next look for a vent from the crankcase area out through the front corner of the oil pan. If there is no vent the block is 1933-34. If there is a vent it is 1935 or later. As a matter of interest, the 1936 engines were the first to use insert bearings. Both insert and babbitt bearings were used throughout 1936. The insert bearing engines can be identified by LB cast at the top of the left front face of the block or by the letters LB stamped into the surface where the intake manifold attaches. Some engines were not stamped and in other cases people tried to inflate the price of their blocks by stamping LB into them when they were sold. Be careful. Now check for the location of the water pumps. If the water pumps mount on the block the engine is 1937 or later. All engines beginning in 1937 were inserts. Frequently you will encounter a 1937 block with factory block off plates held on by two bolts over the water pump passage at the front of the block as it was common for Ford dealers to install this engine as a replacement in the earlier cars. Of course there will be slight transition periods at model change over with the older blocks usually going into the commercial vehicles. There may be subtle differences between the 1933-34 and the 1935-36 engines but I am knowledgeable enough about these years to know what they are. The casting numbers on the flywheel housing will also help identify the exact year of the engine. Post what you find and someone can probably further identify the engine.
Charlie Stephens