stuck GG keg!?!?

I recently aquired two Golden Gate Kegs that I would like to use for cask conditioning and serving. I have the taps and new gaskets. Issue being, I cannot figure how to get the threaded retainer ring off in order to sanitize. Do I need a special tool? I s'pose I could fabricate one, but rather have proper tool, if one even exists. It must! Why can I not find one anywhere?? Also the bung is wood and wont come out. Is this due to swelling? Would a cork or rubber bung be an acceptable replacement? Thanks yall

Does your keg look like this?



Those are McMenamin's kegs, and they use Golden Gate. As far as I know, those rings don't come off, and all cleaning and such is done through the bunghole. (lol) That wooden bung is usually broken off and another one is installed after beer has been put back in. A rubber bung may be OK, but I'm not 100% sure on that. Also look up Hoff-Stevens kegs, they are similarly made.