I have been successful in removing them by grinding the head of a bolt to fit the slot in the retaining ring, and fit the bolt to a slide hammer... work it out one side at a time.
good idea i did not think about a slide hammer i will do that in the morning be fore we open the shop thanks
"i reject your reality and substitute my own" - adam savage. i suspect my final words maybe "well shit, that didnt work"
instead of perfection some times we just have to accept practicality