I'll ad another to the "that also happened to me" posts.
I broke the top intake manifold screw off flush with the head for the #2 carb.
This all started off in just trying to replace the intake manifolds with new ones, and I wasn't going to allow it to turn into a full fledged rebuild (that's for a later time).
I used a small right angle drill to get it started, then started turning the EZ-out into it....SNAP!
Ok, long story short, I went and bought a couple of those cobalt tipped drill bits with the funny shaped heads on them (it kinda resembles a mushroom) and drilled into the head
around the screw itself.
Once removed, I went and purchased a stud to install in the screws place, and just JB-welded it into the now enlarged hole where the screw once resided.
After letting it sit for a full 24 hours to cure, I installed the manifolds (I also replaced the screws on the other manifolds with studs as well), then just screwed some flanged nuts onto those studs.
Almost a full two years and roughly 20K later, and it's still holding solid.
Plus being on the #2 carb the repair can't be seen.
Besides, the manifold hides the repair anyway.