I think you are on the right track with a cam similar to the 308R to get the performance that you want. A friend of mine, thatdarncat on this forum, is doing a very similar build. He just got a pair of Comp cams for his engine that use the 8594 Comp lobe on intake and exhaust, with 114 LSA. This is a .708" lift, 277@.050" cam. The duration sounds like a lot, but remember with the very low 1.3:1 rocker ratio of the SOHC you need more duration at .050" lobe lift to get the same valve action as a standard FE with 1.76:1 rockers. Comp actually provides that data in their spec sheet; they call it " check dur tappet @.050 ", and for this cam it is 266 degrees. So, you can expect this cam to behave duration wise about the same as a 266 @ .050" standard FE cam.
I'd expect a cam like this to idle around 1000 RPM with carbs, and make 700-730 HP with your setup, assuming you have decent compression. What have you set up the compression at? You will need some good compression, like 11.5:1 or higher.
Edit: Oops, just saw that you are running 10:1 compression. That will cost you some power, and maybe the next step down on the cam would be better. This is the 8592 lobe, with .702" lift, 269@.050", and that check dur tappet @ .050" number is 257@.050". I'll email you some data on the cams so you can take a look at the options...