Note that there were 20 and 24 tooth versions of the 350EW pump gear. Douglas apparently changed to a 20 tooth gear of a slightly coarser pitch (not sure when) to get more depth of engagement and alleviate the stripped gear problem. The two types are not interchangeable; unless you replace the mating drive worm at the same time. So if replacing the oil pump gear, make a note of the number of teeth and replace with one of the same tooth count. I can not get a tooth count off of these, but the look like the 24 tooth gears. Which are the type that often most need replacing.
-Doug