Hello Don, good to see you. Yes, as you mentioned the "600" had a six speed transmission, as the "500" was introduced in 1954, with the old "LA" 4 speed, which really cooled off some "500" sales. We had a "500" on the farm mixed in with the others, I really enjoyed running it. (but then what Case didn't I enjoy! :)
Hope all is good at your ranch Don.