Gran Compe center pulls
 

Looks like the eye bolt that holds the post of the pad is a bit smaller in diameter than modern brake pads. Can someone recommend eye bolts that I could use in place so I can run modern brake pads?

I have a set that's still rolling with the original pads- but I will be getting to the point of needing new shoes.

I think the conventional wisdom with these has been to use non- threaded post shoes and sand them down to fit.

Oh wow really? Sanding them down seems like it would be a lot of effort to take off that much material haha.
I was thinking that there would be some take offs from another brake set that would fit well and fit modern brake posts.

^^^ What Golden Boy said- I have a pair of GC450s and needed up replace the pads... It was a huge PITA, but I bought a pair of kool stop cross pads (with smooth post) and filed the posts down to the point that they could fit. If you have the right tools it will probably be a cinch; I stuck a bastard file in the bench vise and the put the end of the smooth post in a cordless drill and went to town. Eventually it got the job done.