D353 counter bore.

So we're trying to sort out our d353 spacer plate deck. #4 cylinder deck is in terrible shape.
The bright side is it looks to have been cut and counter bore inserts installed on that cylinder and few other cylinders.
is there a standard for these? Or are they a custom job by who ever did it?
Also what would be a safe way to remove the insert?

I'll try to post a pic
But I've been having uploading to the site recently

D353 counter bore.