All,
Update: Although I could not initially see any part numbers on the forks, your responses told me they are numbered so I took a closer look. With a high-powered flashlight at just the right angle I could barely see it. My transmission has two identical forks for 1-2, and 3-4 gears and that is part number 590514 which from the sources you led me to indicates it is an earlier transmission - most likely a '41 which came new with the truck. Comparing my part to the photos from the supplier confirmed it. The truck has a '53 motor in it and I assumed the transmission came with it but apparently not. I was reminded what they say about assumptions.
In any case, the replacement fork is on the way and I should be able to test-drive it again soon - right after polishing up the guide bar so the fork will move back and forth freely.
Thank you so much for the leads!
Now back to work work.
