The photo makes the pumps look like they are different sizes. They are in fact the same size, and differ only in the casting shape in the upper section.
the one without the casting number probably the right one for 1924, according to the ones on my Johnson Light Twins. The 1922-23 motors have the pump with the casting number on the starboard side. Hope this helps.
Best,
PM T2
He's livin' in his own private Idaho..... I hope to go out quietly in my sleep, like my grand-dad did..... and not screaming, like the passengers in his car...