I believe "Hydro" is just part of the Hurst name. Catalina & GP would have the RHM-375, the Roto-HydraMatic 3-spd. Star Chief & Bonne would have the Super HydraMatic 4-speed. Pretty positive this was only available for the more likely performance cars; the Cat & the GP, not the Bonnes. I'm not sure if it was available before '64. Jeff- please consider PMing me if you come up with a price; I have a '64 GP. Thanks.
I had a Hurst Dual Gate in my coupe about 35 years ago. It worked really well. I gave it to a friend when I went to a different engine/trans combo and column shifter. I would recommend it.
i had one in my 64 nova sedan for close to 20 years. replaced it with a b&m quick click. the dual gate was better!
Throw it on Feebay with an insane reserve, but leave the "make an offer" option open. You can always lower the reserve if it gets up high enough that you walk away with a smile. If nothing else, you'll get an idea of value, because it's only worth what someone will pay.