Kudos for your success outside the box!
As for your next question, it's kind an interesting problem. Might you able to disassemble the rest of the plunger, leaving the pin and the small shaft (37) permanently in place? If so, you could simply treat parts 24, 37 and 38 as a single unit. What I can see of the parts diagram doesn't seem to show any features on 37 that would permanently hold on to the other parts (31 thru 36).
If you absolutely have to remove 38, you might be able to do so by drilling a smaller diameter hole from the opposite side and using some kind of drift to knock it out. By making a smaller hole, whatever feature keeps the pin from going in too deeply would still be largely there.
I thought I might be able to disassemble the rest of the plunger based on the diagram, but I cannot for the life of me see how I can. I have looked over the entire plunger and I cannot see how it comes apart. The rest of the diagram (below) makes me think that part 32 is another pin that holds the outside of the plunger on, but I don't see it on my plunger. I think this might be one of those parts is actually "different" than what is shown. They even say that in the manual that some parts might be different.
Thinking about how the actuation of the plunger works and the diagram, the handle 31 has to be attached to 37 somehow or else the spring would actually be pushing the plunger away instead of pulling it closer. Maybe the handle screws into 37?
If I have to start cutting and or modifying things, I will probably just live with it. I have put the plunger and the yoke in my parts cleaner, and it seems to be moving slightly better, but I can tell its not totally clean inside because it still spits out rusty colored oil and has some drag whenever I actuate the plunger.
You could drill pin #38 and maybe use an ezy-out.
Or drill through the full length of the pin but not the hole it is in, (might be hard to gauge). Then use grease and a neat fitting punch to hydraulic it out.
Or drill it as close as you can to the diameter and just collapse the wall.
Or drill it oversize and replace with a larger pin.
Cheers Phil
This scares me as I have no idea how deep the whole goes. I might drill right through the piece that is being held in place.