707 Hell Cat, what does it mean?

I saw the same episode of the flathead rebuild, I liked the results, that motor had a COOL factor. For me, that's what I like about vintage Mopars. The other day I was fueling up the wife's Jeep, saw a newer challenger, asked the guy how he liked it. He said he loved it, waited 4 years to get it (it was a 2010) because they only built 833 in that color with the transmission that it had. I guess that makes it rare, and it worked for him, not for me though, not nearly as cool as everything I see here on FABO!!!