Removing Bolts from Leaf Spring Cup

[dtep]

I'm beginning the process of removing the rear suspension from my wife's 68 RS to clean it up and replace the 50 year old rubber parts.  As expected, the bolts in the leaf spring cups just spin so I'm going to have to either drill them out or grind off the heads.  I've never seen what is under the cup as far as the size of the holes where the j-clips are inserted.  Is the hole big enough to remove the old J-clips and remains of the bolts, especially if I grind off the bolt heads?

I'm open to any other suggestions as well.  Thanks!

[dtep]

Never mind!!  I've searched the Internet for this numerous times and never found what I was looking for.  As soon as I posted here, I searched again and found that, yes, the holes are big enough.

[Everett#2390]

Yes, the holes have to be large enough for an assembled clip install.
I bought a couple flea market 9/16 box end wrenches and heated and bent them to fit into hole and place box end over nut to hold.
You will need two different lengths of bending, but worked great for removing/installing bolts.
Coat threads with anti-seize for later in life usage.