Yes, this isn't all that uncommon. Before I forget, you can get genuine AC Delco eye bolts/bushings on Amazon. They're original quality and cheaper than the other suppliers by about $10 each. I mentioned this about a month ago and am using these in my 1952 1/2 ton.

As for the hole being oblong, you could do what you've suggested. It may not stay in place or stay solid for long, however. If you have a propane torch, here is another idea: Stay-Brite silver bearing solder is one of the hardest solders available and it melts at something around 500 degrees. This temp shouldn't be enough to alter the temper of your spring nor damage your bushing. Just be very careful not to get any inside the bushing The company claims Stay-Brite 8 is stronger than a brazed joint in some cases. At any rate, if you can use some imagination and figure out how to fill the gap with this, it might stay in place longer. The eye bolt and its bushing take a lot of vibration after all. Good luck!
Jon

~ Jon
1952 1/2 ton with 1959 235 | T5 with 3.07 rear end