I had to go look at the brackets from my donor with the K6476 bushings I have after seeing this post. Mine look fine. Whew! Don't do that!
My guess is your donor didn't have the correct brackets to begin with, they do look like conduit clamps. Might explain why the rubber bushings were trashed.
Glad you were able to make it work and are happy with the results. Nice lookin' ride...