The cam you say you already have looks a lot like the GM "HOT" cam p/n 12370846. GM installs this cam in their ZZ383 crate motor and it pumps out 425 hp @ 5400.
This cam is one of Dennis Moore's recommendations from his book.
Hot cam specs:
Duration @ .05: 222/230
Lift w/1.5:1 rockers: 509/528